Drop support for Python 2 and 3.4

Some of our development dependencies, like Sphinx, have already dropped
support for Python 2. This makes it harder for this project to update
its dependencies. Since Python 2 only has a few more months to live, I
think it's fine to drop support now.

Python 3.4 has already reached its end-of-life date.

Python-RSA now only supports Python 3.5 and newer. Python 3.5 support is
intended to last until its end-of-life date of 2019-09-13:
https://devguide.python.org/#status-of-python-branches

8 files changed, 246 insertions, 196 deletions

diff --git a/.travis.yml b/.travis.yml
index 9b4da02..d27ebaf 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,23 +1,22 @@
 language: python
+dist: bionic   # required for Python >= 3.7
 cache: pip
 
 # Environment changes have to be manually synced with 'tox.ini'.
 # See: https://github.com/travis-ci/travis-ci/issues/3024
 
-# Python 3.7 is not yet supported by Travis CI.
-# See: https://github.com/travis-ci/travis-ci/issues/9815
-
 python:
-  - "2.7"
-  - "3.4"
-  - "3.5"
   - "3.6"
-  - "3.7-dev"
+  - "3.7"
+
+matrix:
+  include:
+    - python: 3.5
+      dist: xenial  # Bionic has no Python 3.5
 
-# This is blocked by https://github.com/pypa/pipenv/issues/2449,
-# also see https://github.com/pypa/pipenv/projects/7
-#  - "pypy"
-  - "pypy3.5"
+    # Disabled, see https://github.com/sybrenstuvel/python-rsa/issues/131
+    #- python: pypy3.5
+    #  dist: xenial  # Bionic has no Python 3.5
 
 install:
   - pip install pipenv
diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index f8ed650..cbc62fb 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -1,6 +1,13 @@
 Python-RSA changelog
 ========================================
 
+Version 4.1 - in development
+----------------------------------------
+
+- Dropped support for Python 2 and 3.4.
+- Move to Python 3.7 in Pipfile (so `pipenv install` creates a Python 3.7 virtualenv).
+
+
 Version 4.0 - released 2018-09-16
 ----------------------------------------
 
diff --git a/Pipfile b/Pipfile
index 0411098..a03274c 100644
--- a/Pipfile
+++ b/Pipfile
@@ -15,9 +15,5 @@ pytest = "*"
 pytest-cov = "*"
 pathlib2 = {version = "*", markers="python_version < '3.6'"}
 
-# Required by pytest, not sure why it's not being picked up.
-funcsigs = {version = "*", markers="python_version < '3.3'"}
-scandir = {version = "*", markers="python_version < '3.3'"}
-
 [requires]
-python_version = "3.6"
+python_version = "3.7"
diff --git a/Pipfile.lock b/Pipfile.lock
index 3546a6c..6a399e6 100644
--- a/Pipfile.lock
+++ b/Pipfile.lock
@@ -1,11 +1,11 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "6de821570183c80777f192330ab933aeab96f259a4c32a50c9e3731b3333eee2"
+            "sha256": "65309370bad59af42cbf3b538e9a050dece94209b8b9657eb4e9f1ca8feedda4"
         },
         "pipfile-spec": 6,
         "requires": {
-            "python_version": "3.6"
+            "python_version": "3.7"
         },
         "sources": [
             {
@@ -18,11 +18,11 @@
     "default": {
         "pyasn1": {
             "hashes": [
-                "sha256:b9d3abc5031e61927c82d4d96c1cec1e55676c1a991623cfed28faea73cdd7ca",
-                "sha256:f58f2a3d12fd754aa123e9fa74fb7345333000a035f3921dbdaa08597aa53137"
+                "sha256:3bb81821d47b17146049e7574ab4bf1e315eb7aead30efe5d6a9ca422c9710be",
+                "sha256:b773d5c9196ffbc3a1e13bdf909d446cad80a039aa3340bcad72f395b76ebc86"
             ],
             "index": "pypi",
-            "version": "==0.4.4"
+            "version": "==0.4.6"
         }
     },
     "develop": {
@@ -35,31 +35,31 @@
         },
         "atomicwrites": {
             "hashes": [
-                "sha256:0312ad34fcad8fac3704d441f7b317e50af620823353ec657a53e981f92920c0",
-                "sha256:ec9ae8adaae229e4f8446952d204a3e4b5fdd2d099f9be3aaf556120135fb3ee"
+                "sha256:03472c30eb2c5d1ba9227e4c2ca66ab8287fbfbbda3888aa93dc2e28fc6811b4",
+                "sha256:75a9445bac02d8d058d5e1fe689654ba5a6556a1dfd8ce6ec55a0ed79866cfa6"
             ],
-            "version": "==1.2.1"
+            "version": "==1.3.0"
         },
         "attrs": {
             "hashes": [
-                "sha256:10cbf6e27dbce8c30807caf056c8eb50917e0eaafe86347671b57254006c3e69",
-                "sha256:ca4be454458f9dec299268d472aaa5a11f67a4ff70093396e1ceae9c76cf4bbb"
+                "sha256:69c0dbf2ed392de1cb5ec704444b08a5ef81680a61cb899dc08127123af36a79",
+                "sha256:f0b870f674851ecbfbbbd364d6b5cbdff9dcedbc7f3f5e18a6891057f21fe399"
             ],
-            "version": "==18.2.0"
+            "version": "==19.1.0"
         },
         "babel": {
             "hashes": [
-                "sha256:6778d85147d5d85345c14a26aada5e478ab04e39b078b0745ee6870c2b5cf669",
-                "sha256:8cba50f48c529ca3fa18cf81fa9403be176d374ac4d60738b839122dfaaa3d23"
+                "sha256:af92e6106cb7c55286b25b38ad7695f8b4efb36a90ba483d7f7a6628c46158ab",
+                "sha256:e86135ae101e31e2c8ec20a4e0c5220f4eed12487d5cf3f78be7e98d3a57fc28"
             ],
-            "version": "==2.6.0"
+            "version": "==2.7.0"
         },
         "certifi": {
             "hashes": [
-                "sha256:339dc09518b07e2fa7eda5450740925974815557727d6bd35d319c1524a04a4c",
-                "sha256:6d58c986d22b038c8c0df30d639f23a3e6d172a05c3583e766f4c0b785c0986a"
+                "sha256:046832c04d4e752f37383b628bc601a7ea7211496b4638f6514d0e5b9acc4939",
+                "sha256:945e3ba63a0b9f577b1395204e13c3a231f9bc0223888be653286534e5873695"
             ],
-            "version": "==2018.10.15"
+            "version": "==2019.6.16"
         },
         "chardet": {
             "hashes": [
@@ -70,49 +70,48 @@
         },
         "coverage": {
             "hashes": [
-                "sha256:03481e81d558d30d230bc12999e3edffe392d244349a90f4ef9b88425fac74ba",
-                "sha256:0b136648de27201056c1869a6c0d4e23f464750fd9a9ba9750b8336a244429ed",
-                "sha256:0bf8cbbd71adfff0ef1f3a1531e6402d13b7b01ac50a79c97ca15f030dba6306",
-                "sha256:10a46017fef60e16694a30627319f38a2b9b52e90182dddb6e37dcdab0f4bf95",
-                "sha256:198626739a79b09fa0a2f06e083ffd12eb55449b5f8bfdbeed1df4910b2ca640",
-                "sha256:23d341cdd4a0371820eb2b0bd6b88f5003a7438bbedb33688cd33b8eae59affd",
-                "sha256:28b2191e7283f4f3568962e373b47ef7f0392993bb6660d079c62bd50fe9d162",
-                "sha256:2a5b73210bad5279ddb558d9a2bfedc7f4bf6ad7f3c988641d83c40293deaec1",
-                "sha256:2eb564bbf7816a9d68dd3369a510be3327f1c618d2357fa6b1216994c2e3d508",
-                "sha256:337ded681dd2ef9ca04ef5d93cfc87e52e09db2594c296b4a0a3662cb1b41249",
-                "sha256:3a2184c6d797a125dca8367878d3b9a178b6fdd05fdc2d35d758c3006a1cd694",
-                "sha256:3c79a6f7b95751cdebcd9037e4d06f8d5a9b60e4ed0cd231342aa8ad7124882a",
-                "sha256:3d72c20bd105022d29b14a7d628462ebdc61de2f303322c0212a054352f3b287",
-                "sha256:3eb42bf89a6be7deb64116dd1cc4b08171734d721e7a7e57ad64cc4ef29ed2f1",
-                "sha256:4635a184d0bbe537aa185a34193898eee409332a8ccb27eea36f262566585000",
-                "sha256:56e448f051a201c5ebbaa86a5efd0ca90d327204d8b059ab25ad0f35fbfd79f1",
-                "sha256:5a13ea7911ff5e1796b6d5e4fbbf6952381a611209b736d48e675c2756f3f74e",
-                "sha256:69bf008a06b76619d3c3f3b1983f5145c75a305a0fea513aca094cae5c40a8f5",
-                "sha256:6bc583dc18d5979dc0f6cec26a8603129de0304d5ae1f17e57a12834e7235062",
-                "sha256:701cd6093d63e6b8ad7009d8a92425428bc4d6e7ab8d75efbb665c806c1d79ba",
-                "sha256:7608a3dd5d73cb06c531b8925e0ef8d3de31fed2544a7de6c63960a1e73ea4bc",
-                "sha256:76ecd006d1d8f739430ec50cc872889af1f9c1b6b8f48e29941814b09b0fd3cc",
-                "sha256:7aa36d2b844a3e4a4b356708d79fd2c260281a7390d678a10b91ca595ddc9e99",
-                "sha256:7d3f553904b0c5c016d1dad058a7554c7ac4c91a789fca496e7d8347ad040653",
-                "sha256:7e1fe19bd6dce69d9fd159d8e4a80a8f52101380d5d3a4d374b6d3eae0e5de9c",
-                "sha256:8c3cb8c35ec4d9506979b4cf90ee9918bc2e49f84189d9bf5c36c0c1119c6558",
-                "sha256:9d6dd10d49e01571bf6e147d3b505141ffc093a06756c60b053a859cb2128b1f",
-                "sha256:be6cfcd8053d13f5f5eeb284aa8a814220c3da1b0078fa859011c7fffd86dab9",
-                "sha256:c1bb572fab8208c400adaf06a8133ac0712179a334c09224fb11393e920abcdd",
-                "sha256:de4418dadaa1c01d497e539210cb6baa015965526ff5afc078c57ca69160108d",
-                "sha256:e05cb4d9aad6233d67e0541caa7e511fa4047ed7750ec2510d466e806e0255d6",
-                "sha256:f05a636b4564104120111800021a92e43397bc12a5c72fed7036be8556e0029e",
-                "sha256:f3f501f345f24383c0000395b26b726e46758b71393267aeae0bd36f8b3ade80"
-            ],
-            "version": "==4.5.1"
+                "sha256:08907593569fe59baca0bf152c43f3863201efb6113ecb38ce7e97ce339805a6",
+                "sha256:0be0f1ed45fc0c185cfd4ecc19a1d6532d72f86a2bac9de7e24541febad72650",
+                "sha256:141f08ed3c4b1847015e2cd62ec06d35e67a3ac185c26f7635f4406b90afa9c5",
+                "sha256:19e4df788a0581238e9390c85a7a09af39c7b539b29f25c89209e6c3e371270d",
+                "sha256:23cc09ed395b03424d1ae30dcc292615c1372bfba7141eb85e11e50efaa6b351",
+                "sha256:245388cda02af78276b479f299bbf3783ef0a6a6273037d7c60dc73b8d8d7755",
+                "sha256:331cb5115673a20fb131dadd22f5bcaf7677ef758741312bee4937d71a14b2ef",
+                "sha256:386e2e4090f0bc5df274e720105c342263423e77ee8826002dcffe0c9533dbca",
+                "sha256:3a794ce50daee01c74a494919d5ebdc23d58873747fa0e288318728533a3e1ca",
+                "sha256:60851187677b24c6085248f0a0b9b98d49cba7ecc7ec60ba6b9d2e5574ac1ee9",
+                "sha256:63a9a5fc43b58735f65ed63d2cf43508f462dc49857da70b8980ad78d41d52fc",
+                "sha256:6b62544bb68106e3f00b21c8930e83e584fdca005d4fffd29bb39fb3ffa03cb5",
+                "sha256:6ba744056423ef8d450cf627289166da65903885272055fb4b5e113137cfa14f",
+                "sha256:7494b0b0274c5072bddbfd5b4a6c6f18fbbe1ab1d22a41e99cd2d00c8f96ecfe",
+                "sha256:826f32b9547c8091679ff292a82aca9c7b9650f9fda3e2ca6bf2ac905b7ce888",
+                "sha256:93715dffbcd0678057f947f496484e906bf9509f5c1c38fc9ba3922893cda5f5",
+                "sha256:9a334d6c83dfeadae576b4d633a71620d40d1c379129d587faa42ee3e2a85cce",
+                "sha256:af7ed8a8aa6957aac47b4268631fa1df984643f07ef00acd374e456364b373f5",
+                "sha256:bf0a7aed7f5521c7ca67febd57db473af4762b9622254291fbcbb8cd0ba5e33e",
+                "sha256:bf1ef9eb901113a9805287e090452c05547578eaab1b62e4ad456fcc049a9b7e",
+                "sha256:c0afd27bc0e307a1ffc04ca5ec010a290e49e3afbe841c5cafc5c5a80ecd81c9",
+                "sha256:dd579709a87092c6dbee09d1b7cfa81831040705ffa12a1b248935274aee0437",
+                "sha256:df6712284b2e44a065097846488f66840445eb987eb81b3cc6e4149e7b6982e1",
+                "sha256:e07d9f1a23e9e93ab5c62902833bf3e4b1f65502927379148b6622686223125c",
+                "sha256:e2ede7c1d45e65e209d6093b762e98e8318ddeff95317d07a27a2140b80cfd24",
+                "sha256:e4ef9c164eb55123c62411f5936b5c2e521b12356037b6e1c2617cef45523d47",
+                "sha256:eca2b7343524e7ba246cab8ff00cab47a2d6d54ada3b02772e908a45675722e2",
+                "sha256:eee64c616adeff7db37cc37da4180a3a5b6177f5c46b187894e633f088fb5b28",
+                "sha256:ef824cad1f980d27f26166f86856efe11eff9912c4fed97d3804820d43fa550c",
+                "sha256:efc89291bd5a08855829a3c522df16d856455297cf35ae827a37edac45f466a7",
+                "sha256:fa964bae817babece5aa2e8c1af841bebb6d0b9add8e637548809d040443fee0",
+                "sha256:ff37757e068ae606659c28c3bd0d923f9d29a85de79bf25b2b34b148473b5025"
+            ],
+            "version": "==4.5.4"
         },
         "coveralls": {
             "hashes": [
-                "sha256:ab638e88d38916a6cedbf80a9cd8992d5fa55c77ab755e262e00b36792b7cd6d",
-                "sha256:b2388747e2529fa4c669fb1e3e2756e4e07b6ee56c7d9fce05f35ccccc913aa0"
+                "sha256:9bc5a1f92682eef59f688a8f280207190d9a6afb84cef8f567fa47631a784060",
+                "sha256:fb51cddef4bc458de347274116df15d641a735d3f0a580a9472174e2e62f408c"
             ],
             "index": "pypi",
-            "version": "==1.5.1"
+            "version": "==1.8.2"
         },
         "docopt": {
             "hashes": [
@@ -122,34 +121,25 @@
         },
         "docutils": {
             "hashes": [
-                "sha256:02aec4bd92ab067f6ff27a38a38a41173bf01bed8f89157768c1573f53e474a6",
-                "sha256:51e64ef2ebfb29cae1faa133b3710143496eca21c530f3f71424d77687764274",
-                "sha256:7a4bd47eaf6596e1295ecb11361139febe29b084a87bf005bf899f9a42edc3c6"
+                "sha256:6c4f696463b79f1fb8ba0c594b63840ebd41f059e92b31957c46b74a4599b6d0",
+                "sha256:9e4d7ecfc600058e07ba661411a2b7de2fd0fafa17d1a7f7361cd47b1175c827",
+                "sha256:a2aeea129088da402665e92e0b25b04b073c04b2dce4ab65caaa38b7ce2e1a99"
             ],
-            "version": "==0.14"
+            "version": "==0.15.2"
         },
         "filelock": {
             "hashes": [
-                "sha256:86fe6af56ae08ebc9c66d54ba3398c35b98916d0862d782b276a65816ff39392",
-                "sha256:97694f181bdf58f213cca0a7cb556dc7bf90e2f8eb9aa3151260adac56701afb"
+                "sha256:18d82244ee114f543149c66a6e0c14e9c4f8a1044b5cdaadd0f82159d6a6ff59",
+                "sha256:929b7d63ec5b7d6b71b0fa5ac14e030b3f70b75747cef1b10da9b879fef15836"
             ],
-            "version": "==3.0.9"
-        },
-        "funcsigs": {
-            "hashes": [
-                "sha256:330cc27ccbf7f1e992e69fef78261dc7c6569012cf397db8d3de0234e6c937ca",
-                "sha256:a7bb0f2cf3a3fd1ab2732cb49eba4252c2af4240442415b4abce3b87022a8f50"
-            ],
-            "index": "pypi",
-            "markers": "python_version < '3.3'",
-            "version": "==1.0.2"
+            "version": "==3.0.12"
         },
         "idna": {
             "hashes": [
-                "sha256:156a6814fb5ac1fc6850fb002e0852d56c0c8d2531923a51032d1b70760e186e",
-                "sha256:684a38a6f903c1d71d6d5fac066b58d7768af4de2b832e426ec79c30daa94a16"
+                "sha256:c357b3f628cf53ae2c4c05627ecc484553142ca23264e593d327bcde5e9c3407",
+                "sha256:ea8b7f6188e6fa117537c3df7da9fc686d485087abf6ac197f9c46432f7e4a3c"
             ],
-            "version": "==2.7"
+            "version": "==2.8"
         },
         "imagesize": {
             "hashes": [
@@ -158,162 +148,204 @@
             ],
             "version": "==1.1.0"
         },
+        "importlib-metadata": {
+            "hashes": [
+                "sha256:23d3d873e008a513952355379d93cbcab874c58f4f034ff657c7a87422fa64e8",
+                "sha256:80d2de76188eabfbfcf27e6a37342c2827801e59c4cc14b0371c56fed43820e3"
+            ],
+            "version": "==0.19"
+        },
         "jinja2": {
             "hashes": [
-                "sha256:74c935a1b8bb9a3947c50a54766a969d4846290e1e788ea44c1392163723c3bd",
-                "sha256:f84be1bb0040caca4cea721fcbbbbd61f9be9464ca236387158b0feea01914a4"
+                "sha256:065c4f02ebe7f7cf559e49ee5a95fb800a9e4528727aec6f24402a5374c65013",
+                "sha256:14dd6caf1527abb21f08f86c784eac40853ba93edb79552aa1e4b8aef1b61c7b"
             ],
-            "version": "==2.10"
+            "version": "==2.10.1"
         },
         "markupsafe": {
             "hashes": [
-                "sha256:a6be69091dac236ea9c6bc7d012beab42010fa914c459791d627dad4910eb665"
-            ],
-            "version": "==1.0"
+                "sha256:00bc623926325b26bb9605ae9eae8a215691f33cae5df11ca5424f06f2d1f473",
+                "sha256:09027a7803a62ca78792ad89403b1b7a73a01c8cb65909cd876f7fcebd79b161",
+                "sha256:09c4b7f37d6c648cb13f9230d847adf22f8171b1ccc4d5682398e77f40309235",
+                "sha256:1027c282dad077d0bae18be6794e6b6b8c91d58ed8a8d89a89d59693b9131db5",
+                "sha256:24982cc2533820871eba85ba648cd53d8623687ff11cbb805be4ff7b4c971aff",
+                "sha256:29872e92839765e546828bb7754a68c418d927cd064fd4708fab9fe9c8bb116b",
+                "sha256:43a55c2930bbc139570ac2452adf3d70cdbb3cfe5912c71cdce1c2c6bbd9c5d1",
+                "sha256:46c99d2de99945ec5cb54f23c8cd5689f6d7177305ebff350a58ce5f8de1669e",
+                "sha256:500d4957e52ddc3351cabf489e79c91c17f6e0899158447047588650b5e69183",
+                "sha256:535f6fc4d397c1563d08b88e485c3496cf5784e927af890fb3c3aac7f933ec66",
+                "sha256:62fe6c95e3ec8a7fad637b7f3d372c15ec1caa01ab47926cfdf7a75b40e0eac1",
+                "sha256:6dd73240d2af64df90aa7c4e7481e23825ea70af4b4922f8ede5b9e35f78a3b1",
+                "sha256:717ba8fe3ae9cc0006d7c451f0bb265ee07739daf76355d06366154ee68d221e",
+                "sha256:79855e1c5b8da654cf486b830bd42c06e8780cea587384cf6545b7d9ac013a0b",
+                "sha256:7c1699dfe0cf8ff607dbdcc1e9b9af1755371f92a68f706051cc8c37d447c905",
+                "sha256:88e5fcfb52ee7b911e8bb6d6aa2fd21fbecc674eadd44118a9cc3863f938e735",
+                "sha256:8defac2f2ccd6805ebf65f5eeb132adcf2ab57aa11fdf4c0dd5169a004710e7d",
+                "sha256:98c7086708b163d425c67c7a91bad6e466bb99d797aa64f965e9d25c12111a5e",
+                "sha256:9add70b36c5666a2ed02b43b335fe19002ee5235efd4b8a89bfcf9005bebac0d",
+                "sha256:9bf40443012702a1d2070043cb6291650a0841ece432556f784f004937f0f32c",
+                "sha256:ade5e387d2ad0d7ebf59146cc00c8044acbd863725f887353a10df825fc8ae21",
+                "sha256:b00c1de48212e4cc9603895652c5c410df699856a2853135b3967591e4beebc2",
+                "sha256:b1282f8c00509d99fef04d8ba936b156d419be841854fe901d8ae224c59f0be5",
+                "sha256:b2051432115498d3562c084a49bba65d97cf251f5a331c64a12ee7e04dacc51b",
+                "sha256:ba59edeaa2fc6114428f1637ffff42da1e311e29382d81b339c1817d37ec93c6",
+                "sha256:c8716a48d94b06bb3b2524c2b77e055fb313aeb4ea620c8dd03a105574ba704f",
+                "sha256:cd5df75523866410809ca100dc9681e301e3c27567cf498077e8551b6d20e42f",
+                "sha256:e249096428b3ae81b08327a63a485ad0878de3fb939049038579ac0ef61e17e7"
+            ],
+            "version": "==1.1.1"
         },
         "mock": {
             "hashes": [
-                "sha256:5ce3c71c5545b472da17b72268978914d0252980348636840bd34a00b5cc96c1",
-                "sha256:b158b6df76edd239b8208d481dc46b6afd45a846b7812ff0ce58971cf5bc8bba"
+                "sha256:83657d894c90d5681d62155c82bda9c1187827525880eda8ff5df4ec813437c3",
+                "sha256:d157e52d4e5b938c550f39eb2fd15610db062441a9c2747d3dbfa9298211d0f8"
             ],
             "index": "pypi",
-            "version": "==2.0.0"
+            "version": "==3.0.5"
         },
         "more-itertools": {
             "hashes": [
-                "sha256:c187a73da93e7a8acc0001572aebc7e3c69daf7bf6881a2cea10650bd4420092",
-                "sha256:c476b5d3a34e12d40130bc2f935028b5f636df8f372dc2c1c01dc19681b2039e",
-                "sha256:fcbfeaea0be121980e15bc97b3817b5202ca73d0eae185b4550cbfce2a3ebb3d"
+                "sha256:409cd48d4db7052af495b09dec721011634af3753ae1ef92d2b32f73a745f832",
+                "sha256:92b8c4b06dac4f0611c0729b2f2ede52b2e1bac1ab48f089c7ddc12e26bb60c4"
             ],
-            "version": "==4.3.0"
+            "version": "==7.2.0"
         },
         "packaging": {
             "hashes": [
-                "sha256:0886227f54515e592aaa2e5a553332c73962917f2831f1b0f9b9f4380a4b9807",
-                "sha256:f95a1e147590f204328170981833854229bb2912ac3d5f89e2a8ccd2834800c9"
+                "sha256:a7ac867b97fdc07ee80a8058fe4435ccd274ecc3b0ed61d852d7d53055528cf9",
+                "sha256:c491ca87294da7cc01902edbe30a5bc6c4c28172b5138ab4e4aa1b9d7bfaeafe"
             ],
-            "version": "==18.0"
+            "version": "==19.1"
         },
         "pathlib2": {
             "hashes": [
-                "sha256:8eb170f8d0d61825e09a95b38be068299ddeda82f35e96c3301a8a5e7604cb83",
-                "sha256:d1aa2a11ba7b8f7b21ab852b1fb5afb277e1bb99d5dfc663380b5015c0d80c5a"
+                "sha256:2156525d6576d21c4dcaddfa427fae887ef89a7a9de5cbfe0728b3aafa78427e",
+                "sha256:446014523bb9be5c28128c4d2a10ad6bb60769e78bd85658fe44a450674e0ef8"
             ],
             "index": "pypi",
             "markers": "python_version < '3.6'",
-            "version": "==2.3.2"
-        },
-        "pbr": {
-            "hashes": [
-                "sha256:ab94783019179bf48f5784edc63f5bc8328ec5ff93f33591567f266d21ac7323",
-                "sha256:bfcff1a3878eebf559392c2130a17f612a03f96a0d44c3559d9c1e62a4235a2d"
-            ],
-            "version": "==5.0.0"
+            "version": "==2.3.4"
         },
         "pluggy": {
             "hashes": [
-                "sha256:447ba94990e8014ee25ec853339faf7b0fc8050cdc3289d4d71f7f410fb90095",
-                "sha256:bde19360a8ec4dfd8a20dcb811780a30998101f078fc7ded6162f0076f50508f"
+                "sha256:0825a152ac059776623854c1543d65a4ad408eb3d33ee114dff91e57ec6ae6fc",
+                "sha256:b9817417e95936bf75d85d3f8767f7df6cdde751fc40aed3bb3074cbcb77757c"
             ],
-            "version": "==0.8.0"
+            "version": "==0.12.0"
         },
         "py": {
             "hashes": [
-                "sha256:bf92637198836372b520efcba9e020c330123be8ce527e535d185ed4b6f45694",
-                "sha256:e76826342cefe3c3d5f7e8ee4316b80d1dd8a300781612ddbc765c17ba25a6c6"
+                "sha256:64f65755aee5b381cea27766a3a147c3f15b9b6b9ac88676de66ba2ae36793fa",
+                "sha256:dc639b046a6e2cff5bbe40194ad65936d6ba360b52b3c3fe1d08a82dd50b5e53"
             ],
-            "version": "==1.7.0"
+            "version": "==1.8.0"
         },
         "pygments": {
             "hashes": [
-                "sha256:78f3f434bcc5d6ee09020f92ba487f95ba50f1e3ef83ae96b9d5ffa1bab25c5d",
-                "sha256:dbae1046def0efb574852fab9e90209b23f556367b5a320c0bcb871c77c3e8cc"
+                "sha256:71e430bc85c88a430f000ac1d9b331d2407f681d6f6aec95e8bcfbc3df5b0127",
+                "sha256:881c4c157e45f30af185c1ffe8d549d48ac9127433f2c380c24b84572ad66297"
             ],
-            "version": "==2.2.0"
+            "version": "==2.4.2"
         },
         "pyparsing": {
             "hashes": [
-                "sha256:bc6c7146b91af3f567cf6daeaec360bc07d45ffec4cf5353f4d7a208ce7ca30a",
-                "sha256:d29593d8ebe7b57d6967b62494f8c72b03ac0262b1eed63826c6f788b3606401"
+                "sha256:6f98a7b9397e206d78cc01df10131398f1c8b8510a2f4d97d9abd82e1aacdd80",
+                "sha256:d9338df12903bbf5d65a0e4e87c2161968b10d2e489652bb47001d82a9b028b4"
             ],
-            "version": "==2.2.2"
+            "version": "==2.4.2"
         },
         "pytest": {
             "hashes": [
-                "sha256:212be78a6fa5352c392738a49b18f74ae9aeec1040f47c81cadbfd8d1233c310",
-                "sha256:6f6c1efc8d0ccc21f8f6c34d8330baca883cf109b66b3df954b0a117e5528fb4"
+                "sha256:6ef6d06de77ce2961156013e9dff62f1b2688aa04d0dc244299fe7d67e09370d",
+                "sha256:a736fed91c12681a7b34617c8fcefe39ea04599ca72c608751c31d89579a3f77"
             ],
             "index": "pypi",
-            "version": "==3.9.2"
+            "version": "==5.0.1"
         },
         "pytest-cov": {
             "hashes": [
-                "sha256:513c425e931a0344944f84ea47f3956be0e416d95acbd897a44970c8d926d5d7",
-                "sha256:e360f048b7dae3f2f2a9a4d067b2dd6b6a015d384d1577c994a43f3f7cbad762"
+                "sha256:2b097cde81a302e1047331b48cadacf23577e431b61e9c6f49a1170bbe3d3da6",
+                "sha256:e00ea4fdde970725482f1f35630d12f074e121a23801aabf2ae154ec6bdd343a"
             ],
             "index": "pypi",
-            "version": "==2.6.0"
+            "version": "==2.7.1"
         },
         "pytz": {
             "hashes": [
-                "sha256:a061aa0a9e06881eb8b3b2b43f05b9439d6583c206d0a6c340ff72a7b6669053",
-                "sha256:ffb9ef1de172603304d9d2819af6f5ece76f2e85ec10692a524dd876e72bf277"
+                "sha256:26c0b32e437e54a18161324a2fca3c4b9846b74a8dccddd843113109e1116b32",
+                "sha256:c894d57500a4cd2d5c71114aaab77dbab5eabd9022308ce5ac9bb93a60a6f0c7"
             ],
-            "version": "==2018.5"
+            "version": "==2019.2"
         },
         "requests": {
             "hashes": [
-                "sha256:99dcfdaaeb17caf6e526f32b6a7b780461512ab3f1d992187801694cba42770c",
-                "sha256:a84b8c9ab6239b578f22d1c21d51b696dcfe004032bb80ea832398d6909d7279"
+                "sha256:11e007a8a2aa0323f5a921e9e6a2d7e4e67d9877e85773fba9ba6419025cbeb4",
+                "sha256:9cf5292fcd0f598c671cfc1e0d7d1a7f13bb8085e9a590f48c010551dc6c4b31"
             ],
-            "version": "==2.20.0"
-        },
-        "scandir": {
-            "hashes": [
-                "sha256:04b8adb105f2ed313a7c2ef0f1cf7aff4871aa7a1883fa4d8c44b5551ab052d6",
-                "sha256:1444134990356c81d12f30e4b311379acfbbcd03e0bab591de2696a3b126d58e",
-                "sha256:1b5c314e39f596875e5a95dd81af03730b338c277c54a454226978d5ba95dbb6",
-                "sha256:346619f72eb0ddc4cf355ceffd225fa52506c92a2ff05318cfabd02a144e7c4e",
-                "sha256:44975e209c4827fc18a3486f257154d34ec6eaec0f90fef0cca1caa482db7064",
-                "sha256:61859fd7e40b8c71e609c202db5b0c1dbec0d5c7f1449dec2245575bdc866792",
-                "sha256:a5e232a0bf188362fa00123cc0bb842d363a292de7126126df5527b6a369586a",
-                "sha256:c14701409f311e7a9b7ec8e337f0815baf7ac95776cc78b419a1e6d49889a383",
-                "sha256:c7708f29d843fc2764310732e41f0ce27feadde453261859ec0fca7865dfc41b",
-                "sha256:c9009c527929f6e25604aec39b0a43c3f831d2947d89d6caaab22f057b7055c8",
-                "sha256:f5c71e29b4e2af7ccdc03a020c626ede51da471173b4a6ad1e904f2b2e04b4bd"
-            ],
-            "index": "pypi",
-            "markers": "python_version < '3.3'",
-            "version": "==1.9.0"
+            "version": "==2.22.0"
         },
         "six": {
             "hashes": [
-                "sha256:70e8a77beed4562e7f14fe23a786b54f6296e34344c23bc42f07b15018ff98e9",
-                "sha256:832dc0e10feb1aa2c68dcc57dbb658f1c7e65b9b61af69048abc87a2db00a0eb"
+                "sha256:3350809f0555b11f552448330d0b52d5f24c91a322ea4a15ef22629740f3761c",
+                "sha256:d16a0141ec1a18405cd4ce8b4613101da75da0e9a7aec5bdd4fa804d0e0eba73"
             ],
-            "version": "==1.11.0"
+            "version": "==1.12.0"
         },
         "snowballstemmer": {
             "hashes": [
-                "sha256:919f26a68b2c17a7634da993d91339e288964f93c274f1343e3bbbe2096e1128",
-                "sha256:9f3bcd3c401c3e862ec0ebe6d2c069ebc012ce142cce209c098ccb5b09136e89"
+                "sha256:9f3b9ffe0809d174f7047e121431acf99c89a7040f0ca84f94ba53a498e6d0c9"
             ],
-            "version": "==1.2.1"
+            "version": "==1.9.0"
         },
         "sphinx": {
             "hashes": [
-                "sha256:652eb8c566f18823a022bb4b6dbc868d366df332a11a0226b5bc3a798a479f17",
-                "sha256:d222626d8356de702431e813a05c68a35967e3d66c6cd1c2c89539bb179a7464"
+                "sha256:22538e1bbe62b407cf5a8aabe1bb15848aa66bb79559f42f5202bbce6b757a69",
+                "sha256:f9a79e746b87921cabc3baa375199c6076d1270cee53915dbd24fdbeaaacc427"
             ],
             "index": "pypi",
-            "version": "==1.8.1"
+            "version": "==2.1.2"
         },
-        "sphinxcontrib-websupport": {
+        "sphinxcontrib-applehelp": {
             "hashes": [
-                "sha256:68ca7ff70785cbe1e7bccc71a48b5b6d965d79ca50629606c7861a21b206d9dd",
-                "sha256:9de47f375baf1ea07cdb3436ff39d7a9c76042c10a769c52353ec46e4e8fc3b9"
+                "sha256:edaa0ab2b2bc74403149cb0209d6775c96de797dfd5b5e2a71981309efab3897",
+                "sha256:fb8dee85af95e5c30c91f10e7eb3c8967308518e0f7488a2828ef7bc191d0d5d"
             ],
-            "version": "==1.1.0"
+            "version": "==1.0.1"
+        },
+        "sphinxcontrib-devhelp": {
+            "hashes": [
+                "sha256:6c64b077937330a9128a4da74586e8c2130262f014689b4b89e2d08ee7294a34",
+                "sha256:9512ecb00a2b0821a146736b39f7aeb90759834b07e81e8cc23a9c70bacb9981"
+            ],
+            "version": "==1.0.1"
+        },
+        "sphinxcontrib-htmlhelp": {
+            "hashes": [
+                "sha256:4670f99f8951bd78cd4ad2ab962f798f5618b17675c35c5ac3b2132a14ea8422",
+                "sha256:d4fd39a65a625c9df86d7fa8a2d9f3cd8299a3a4b15db63b50aac9e161d8eff7"
+            ],
+            "version": "==1.0.2"
+        },
+        "sphinxcontrib-jsmath": {
+            "hashes": [
+                "sha256:2ec2eaebfb78f3f2078e73666b1415417a116cc848b72e5172e596c871103178",
+                "sha256:a9925e4a4587247ed2191a22df5f6970656cb8ca2bd6284309578f2153e0c4b8"
+            ],
+            "version": "==1.0.1"
+        },
+        "sphinxcontrib-qthelp": {
+            "hashes": [
+                "sha256:513049b93031beb1f57d4daea74068a4feb77aa5630f856fcff2e50de14e9a20",
+                "sha256:79465ce11ae5694ff165becda529a600c754f4bc459778778c7017374d4d406f"
+            ],
+            "version": "==1.0.2"
+        },
+        "sphinxcontrib-serializinghtml": {
+            "hashes": [
+                "sha256:c0efb33f8052c04fd7a26c0a07f1678e8512e0faec19f4aa8f2473a8b81d5227",
+                "sha256:db6615af393650bf1151a6cd39120c29abaf93cc60db8c48eb2dddbfdc3a9768"
+            ],
+            "version": "==1.1.3"
         },
         "toml": {
             "hashes": [
@@ -324,25 +356,39 @@
         },
         "tox": {
             "hashes": [
-                "sha256:217fb84aecf9792a98f93f07cfcaf014205a76c64e52bd7c2b4135458e6ad2a1",
-                "sha256:4baeb3d8ebdcd9f43afce38aa67d06f1165a87d221d5bb21e8b39a0d4880c134"
+                "sha256:dab0b0160dd187b654fc33d690ee1d7bf328bd5b8dc6ef3bb3cc468969c659ba",
+                "sha256:ee35ffce74933a6c6ac10c9a0182e41763140a5a5070e21b114feca56eaccdcd"
             ],
             "index": "pypi",
-            "version": "==3.5.2"
+            "version": "==3.13.2"
         },
         "urllib3": {
             "hashes": [
-                "sha256:41c3db2fc01e5b907288010dec72f9d0a74e37d6994e6eb56849f59fea2265ae",
-                "sha256:8819bba37a02d143296a4d032373c4dd4aca11f6d4c9973335ca75f9c8475f59"
+                "sha256:b246607a25ac80bedac05c6f282e3cdaf3afb65420fd024ac94435cabe6e18d1",
+                "sha256:dbe59173209418ae49d485b87d1681aefa36252ee85884c31346debd19463232"
             ],
-            "version": "==1.24"
+            "version": "==1.25.3"
         },
         "virtualenv": {
             "hashes": [
-                "sha256:2ce32cd126117ce2c539f0134eb89de91a8413a29baac49cbab3eb50e2026669",
-                "sha256:ca07b4c0b54e14a91af9f34d0919790b016923d157afda5efdde55c96718f752"
+                "sha256:6cb2e4c18d22dbbe283d0a0c31bb7d90771a606b2cb3415323eea008eaee6a9d",
+                "sha256:909fe0d3f7c9151b2df0a2cb53e55bdb7b0d61469353ff7a49fd47b0f0ab9285"
+            ],
+            "version": "==16.7.2"
+        },
+        "wcwidth": {
+            "hashes": [
+                "sha256:3df37372226d6e63e1b1e1eda15c594bca98a22d33a23832a90998faa96bc65e",
+                "sha256:f4ebe71925af7b40a864553f761ed559b43544f8f71746c2d756c7fe788ade7c"
+            ],
+            "version": "==0.1.7"
+        },
+        "zipp": {
+            "hashes": [
+                "sha256:4970c3758f4e89a7857a973b1e2a5d75bcdc47794442f2e2dd4fe8e0466e809a",
+                "sha256:8a5712cfd3bb4248015eb3b0b3c54a5f6ee3f2425963ef2a0125b8bc40aafaec"
             ],
-            "version": "==16.0.0"
+            "version": "==0.5.2"
         }
     }
 }
diff --git a/README.md b/README.md
index c5e0f2d..8c43464 100644
--- a/README.md
+++ b/README.md
@@ -23,6 +23,11 @@ or download it from the [Python Package Index](https://pypi.org/project/rsa/).
 The source code is maintained at [GitHub](https://github.com/sybrenstuvel/python-rsa/) and is
 licensed under the [Apache License, version 2.0](https://www.apache.org/licenses/LICENSE-2.0)
 
+Major changes in 4.1
+--------------------
+
+Version 4.0 was the last version to support Python 2 and 3.4. Version 4.1 is compatible with Python 3.5+ only.
+
 
 Major changes in 4.0
 --------------------
diff --git a/doc/installation.rst b/doc/installation.rst
index 32dc257..e8f7170 100644
--- a/doc/installation.rst
+++ b/doc/installation.rst
@@ -1,13 +1,13 @@
 Installation
 ============
 
-Installation can be done in various ways. The simplest form uses pip
-or easy_install. Either one will work::
+Installation can be done in various ways. The simplest form uses pip::
 
     pip install rsa
 
 Depending on your system you may need to use ``sudo pip`` if you want to install
-the library system-wide.
+the library system-wide, or use ``pip install --user rsa`` to install the
+library in your home directory.
 
 Installation from source is also quite easy. Download the source and
 then type::
@@ -25,6 +25,9 @@ GitHub. It also hosts the `issue tracker`_.
 Dependencies
 ------------
 
+Python-RSA is compatible with Python versions 3.5 and newer. The last
+version with Python 2.7 support was Python-RSA 4.0.
+
 Python-RSA has very few dependencies. As a matter of fact, to use it
 you only need Python itself. Loading and saving keys does require an
 extra module, though: pyasn1. If you used pip or easy_install like
@@ -34,17 +37,14 @@ described above, you should be ready to go.
 Development dependencies
 ------------------------
 
-In order to start developing on Python-RSA you need a bit more. Use
-pip to install the development requirements in a virtual environment::
-
-    virtualenv -p /path/to/your-python-version python-rsa-venv
-    . python-rsa-venv/bin/activate
-    pip install -r python-rsa/requirements.txt
+In order to start developing on Python-RSA, use Git_ to get a copy of
+the source::
 
+    git clone https://github.com/sybrenstuvel/python-rsa.git
 
-Once these are installed, use Git_ to get a copy of the source::
+Use pipenv_ to install the development requirements in a virtual environment::
 
-    git clone https://github.com/sybrenstuvel/python-rsa.git
-    python setup.py develop
+    pipenv install --dev
 
 .. _Git: https://git-scm.com/
+.. _pipenv: https://docs.pipenv.org/
diff --git a/setup.py b/setup.py
index ad2603e..2fc08ef 100755
--- a/setup.py
+++ b/setup.py
@@ -44,10 +44,7 @@ if __name__ == '__main__':
               'License :: OSI Approved :: Apache Software License',
               'Operating System :: OS Independent',
               'Programming Language :: Python',
-              'Programming Language :: Python :: 2',
-              'Programming Language :: Python :: 2.7',
               'Programming Language :: Python :: 3',
-              'Programming Language :: Python :: 3.4',
               'Programming Language :: Python :: 3.5',
               'Programming Language :: Python :: 3.6',
               'Programming Language :: Python :: 3.7',
diff --git a/tox.ini b/tox.ini
index 9b034e2..0401412 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 # Environment changes have to be manually synced with '.travis.yml'.
-envlist = py27,py34,py35,py36,p37,pypy
+envlist = py35,py36,p37
 
 [pytest]
 addopts = -v --cov rsa --cov-report term-missing