Ensure virtualenv is upgraded when installing tox. Fixes jaraco/path#188.
Ensure virtualenv is upgraded when installing tox. Fixes jaraco/path#188.

jaraco/jaraco.classes,yougov/pmxbot,yougov/pmxbot,jaraco/keyring,jaraco/calendra,jaraco/jaraco.itertools,jaraco/zipp,pwdyson/inflect.py,jaraco/backports.functools_lru_cache,jaraco/jaraco.context,jazzband/inflect,pytest-dev/pytest-runner,jaraco/jaraco.logging,jaraco/jaraco.text,jaraco/jaraco.collections,jaraco/jaraco.stream,python/importlib_metadata,jaraco/portend,yougov/pmxbot,jaraco/jaraco.path,jaraco/tempora,jaraco/irc,jaraco/hgtools,jaraco/jaraco.functools