requirements.txt hangs with pip install -r requirements.txt #585

Just cloned and merged a fork of the latest python-docs-samples repo.
Cannot successfully get requirements.txt to complete.
I may have to recreate the virtualenv fresh because the 0.18.1 version is what is active in the current virtualenv. Your latest PB is 0.20.0 and I should be using that.

Update: This runs correctly in a new ve.
The previous ve was unhappy to have a new gcp setup overlaid.
My env is pretty fat at this point with paths and such.

What would be nice is to be able to build a slimmer package with only the GCP services needed for a project rather than everything that is in the python-docs-samples repo. It has a lot of stuff I am not using at the moment.