pip install breaks pip / fails

[alex-r-bigelow]

I've googled around and I think there's some kind of dependency problem; after installing flask-sentinel with pip, pip itself breaks (we get this error):
cffi.api.CDefError: 'point_conversion_form_t' has no values explicitly defined: refusing to guess which integer type it is meant to be (unsigned/signed, int/long)

It looks to be related to this discussion: graphite-project/graphite-web#1721, which in turn references others—but all of these look like they should be fixed at this point in time.

I'm able to fix pip with apt-get remove python-cffi, per this thread, but then attempts to pip install flask-sentinel result in some kind of cryptography compile error.

This issue may need to be passed along to whatever dependency is causing it, but as pip install flask-sentinel is the entry point for the problem for me, this seems like the best place to file the issue.

[alex-r-bigelow]

I think I may have figured it out... this seems to work:

apt-get install libssl-dev
pip install flask-sentinel