Comment 2 for bug 1535134

Had the same problem trying to run the neutron test suite on Ubuntu 15.10. A new pip version fixed it for me.

Ubuntu ships with pip 1.5.6. But according to the pip docs, you need at least version 6 to parse one of the openstack requirements.txt
https://pip.pypa.io/en/stable/reference/pip_install/#requirement-specifiers