Here's the output of pip freeze, for reference:

[root@machine ~]# pip freeze
argparse==1.2.1
autobahn==0.8.10
cffi==1.5.2
characteristic==14.3.0
pika==0.9.13
pyasn1==0.1.7
pyasn1-modules==0.0.8
pycparser==2.14
pycrypto==2.6.1
pyOpenSSL==0.12
pysnmp==4.2.5
requests==2.7.0
service-identity==14.0.0
six==1.7.3
Twisted==14.0.0
version-utils==0.2.2
wheel==0.24.0
zope.interface==4.1.1

If you've got the same or better versions of the relevant packages installed, I'd try a 

pip -vvv install --upgrade --force-reinstall cffi

 

just to see if there are perhaps errors that pip was masking, and go from there.