demandimport: blacklist distutils.msvc9compiler (issue4475) This module depends on _winreg, which is windows-only. Recent versions of setuptools load distutils.msvc9compiler and expect it to ImportError immediately when on non-Windows platforms, so we need to let them do that. This breaks in an especially mystifying way, because setuptools uses vars() on the imported module. We then throw an exception, which vars doesn't pick up on well. For example: In [3]: class wat(object): ...: @property ...: def __dict__(self): ...: assert False ...: In [4]: vars(wat()) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) <ipython-input-4-2781ada5ffe6> in <module>() ----> 1 vars(wat()) TypeError: vars() argument must have __dict__ attribute Which is similar to the problem we run into.