1 files changed, 4 insertions, 2 deletions
diff --git a/setuptools/sandbox.py b/setuptools/sandbox.py
index 213cebff..b8b1bac1 100755
--- a/setuptools/sandbox.py
+++ b/setuptools/sandbox.py
@@ -98,8 +98,8 @@ class UnpickleableException(Exception):
     """
     An exception representing another Exception that could not be pickled.
     """
-    @classmethod
-    def dump(cls, type, exc):
+    @staticmethod
+    def dump(type, exc):
         """
         Always return a dumped (pickled) type and exc. If exc can't be pickled,
         wrap it in UnpickleableException first.
@@ -107,6 +107,8 @@ class UnpickleableException(Exception):
         try:
             return pickle.dumps(type), pickle.dumps(exc)
         except Exception:
+            # get UnpickleableException inside the sandbox
+            from setuptools.sandbox import UnpickleableException as cls
             return cls.dump(cls, cls(repr(exc)))