The issue is that the messaging plugins are defined as setuptools
entry-points, and those live in the .egg-info directory. If you're developing
locally, that directory is usually present in pwd due to `python setup.py
develop` or python setup.py egg-info. But in the spec file, we install to a
directory that is not in the PYTHONPATH. This change re-enables the -F
option but also specifies the PYTHONPATH so that the entry-points are found and
the tests pass.
This should fix T874.