jaraco/setuptools — pull request #18 by dstufft (2014-12-15 12:43:55+00:00)
Title: Define a __hash__ on the packaging.version.Version subclasses

In Python 3.x a subclass will not inherent the ``__hash__`` method from the parent classes if the subclass defines a ``__eq__`` method. This means that without defining our own ``__hash__`` the ``SetuptoolsVersion`` classes are unhashable.