test_installs_all_data_files fails with vim .swo files
I received the following failure:
AssertionError: setup.py doesn't install stem/stem/.prereq.py.swo
It might be useful to have a set of file types to include, rather than exclude, but this is a larger refactor (but something to think about if this error happens with another file type).
Another possible refactor is to extract this list as it is used in several different places (so we have one single list of file types that we exclude). Specifically, we have the same logic in test/integ/installation.py and test/unit/installation.py, for example.