When exceuting tox: 
09:45:18 Traceback (most recent call last):09:45:18 File "/w/workspace/sfc-verify-python-fluorine/venv-tox/bin/tox", line 5, in <module>09:45:18 from pkg_resources import load_entry_point*09:45:18* File "/w/workspace/sfc-verify-python-fluorine/venv-tox/lib/python2.7/site-packages/pkg_resources.py", line 3007, in <module>09:45:18 working_set.require(_requires_)09:45:18 File "/w/workspace/sfc-verify-python-fluorine/venv-tox/lib/python2.7/site-packages/pkg_resources.py", line 728, in require*09:45:18* needed = self.resolve(parse_requirements(requirements))09:45:18 File "/w/workspace/sfc-verify-python-fluorine/venv-tox/lib/python2.7/site-packages/pkg_resources.py", line 626, in resolve*09:45:18* raise DistributionNotFound(req)09:45:18 pkg_resources.DistributionNotFound: virtualenv>=1.11.2