Handle python eggs in install python scripts
I just had to debug why pyfftw wasn't installing, this is the summary of what I found.
pyfftw installs as a python egg to this path: install/lib/python3.6/site-packages/pyFFTW-0.10.4-py3.6-macosx-10.9-x86_64.egg/pyfftw
The install python module script didn't find it and was skipping it for the install (I'm not sure why it didn't fail). I don't have time right now to teach common-sb about python eggs right now, so I'm reporting this instead. My temporary fix is to pass the --single-version-externally-managed
flag to make pyfftw not install in the egg folder.