Also consider using Conda - to replace and simplify use of venv and pip. http://stuarteberg.github.io/conda-docs/_downloads/conda-pip...
If I had to vote on: "There should be one-- and preferably only one --obvious way to do it." for Python dev, I would choose Conda so hard.
Instead, I recommend creating whatever environment you want, activating it, and then running python setup.py develop or pip install -e . so that your package is installed in develop mode in that environment.