I'm not sure if I agree... What if the `import matplotlib` works because it's available somewhere else in `$PYTHONPATH`?
The sanity check paths are there for a good reason, and have helped numerous times before in catching actual problems with the build/installation.

It does look kind of ugly, I agree. One solution to that would be defining a proper default sanity check in `PythonPackage`, that checks for the `site-packages` dir and the `.egg`.
Then the 'custom' `sanity_check_paths` can be removed from a lot of Python package easyconfigs, without sacrificing the actual checks.

I believe @wpoely86 was up for that (at some point in the near distant future).