cffi builds the name of the shared object using a long byte string that contains the version of cffi. This causes an issue for other modules that depend on cffi and distribute wheels, as the wheel's compiled shared object name is dependent on the version of cffi that was used. If cffi is updated (e.g. from 0.8.1 to 0.8.2) then the wheel will no longer contain a valid shared object and the user will be forced to recompile (if they can).
A possible workaround would be strictly pinning the cffi dependency, but that's not desirable.