With pip + upper-constraints we're nearly always over installing all
python packages because we no longer support a range, we support
*exactly* one version.
This removes a bunch of the gratuitous package installs which we're
going to install over, lxml, numpy, libvirt. All of these we had
coming from packages in the past for speed concerns, but upper
constraints removes that.
It also ensures that all the headers to build all those are in
general, so they are guarunteed available at all times.
Change-Id: Ia76de730d65c84d81c4fb2c980ae1b4d595f9f5b
5f8133caac