[BUG] tox congratulates me even if I ^C it

[asottile]

Fortunately it exits nonzero so this is more of a cosmetic issue than anything else:

$ tox -e py37
GLOB sdist-make: /home/asottile/workspace/pluggy/setup.py
py37 create: /home/asottile/workspace/pluggy/.tox/py37
^CERROR: got KeyboardInterrupt signal
___________________________________ summary ____________________________________
  py37: commands succeeded
  congratulations :)
$ echo $?
2
$ tox --version
3.8.6 imported from /home/asottile/opt/venv/lib/python3.6/site-packages/tox/__init__.py
registered plugins:
    tox-virtualenv-no-download-1.1.0 at /home/asottile/opt/venv/lib/python3.6/site-packages/tox_virtualenv_no_download.py
    tox-pip-extensions-1.6.0 at /home/asottile/opt/venv/lib/python3.6/site-packages/tox_pip_extensions.py