Can't roll back cryptography; was not uninstalled

Command "/opt/caldavd/CalendarServer-7.0/.develop/virtualenv/bin/python -c "import setuptools, tokenize;__file__='/tmp/pip-build-M1eqq0/cryptography/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-bXjSbl-record/install-record.txt --single-version-externally-managed --compile --install-headers /opt/caldavd/CalendarServer-7.0/.develop/virtualenv/include/site/python2.7/cryptography" failed with error code 1 in /tmp/pip-build-M1eqq0/cryptography