Adds a test that was able to reproduce the problem in #1256 (on Python 3.2 at least, on other versions it doesn't appear to be an issue for some reason, probably due to subtle differences in the import implementation between those versions). Fixes the issue more or less in the way I suggested in the issue.
Merge pull request #1256 from embray/issue-1256

AttributeError in _find_pkg_data_path with Python 3.2