Use pypi-mirror instead of jeepyb

Change-Id: I56dffb73526bd56ac544d320d9d6f2baa6175a2a
Remove pip as an argument from mkvenv

We no longer care about or support old pip, because it turns out that
evil happens. Remove it from the mkvenv function.

Change-Id: I27dbef7816eaac856e97ec5a036f6d5ca9b183af
Add wheel mirror structure awareness

We are going to start having wheels in the gate. Having them there
should not break folks who are not using wheels.  Don't start actually
consuming wheels yet, but add awareness about the wheel structure to the
pypi config.

Change-Id: Id29bb1bb31fc1647f8e1ea00bab487e447ba2838
Merge "Use pypi-mirror instead of jeepyb"
Merge "Remove pip as an argument from mkvenv"
Merge "Add wheel mirror structure awareness"