Fix ci path issue

[rmarren1]

Fixes #419

This one was tricky to figure out.

For some reason, the Python 3 venv package behaves differently from the virtualenv package. The current working directory was not included in the PYTHONPATH and needed to be manually added back using sys.path.append. (Not sure why the dash module is available, I think this is because the new default_namespace module is created during execution rather than before).

Just getting rid of python -m venv and using virtualenv works.

Is there a good reason to be using venv rather than virtualenv?

[T4rk1n]

That venv thing was from the circleci example, but we install virtualenv anyway so we don't need it.

venv is stdlib for python >= 3.3

💃