Recent changes in project-config have shown that we leave the system
in an inconsistent state when installing from source. On fedora, we
will have installed the python2 packages, but then used $DIB_PYTHON to
install python3 pip from source!
This tries to clarify the situation. As described in the document,
with package installs, we just install the $DIB_PYTHON packaged
versions.
Source installs want to take over the global namespace. This is the
price you pay for running the latest versions outside package managers
:) The only sane thing seems to be for us to normalise python2 &
python3 versions of pip, setuptools and virtualenv and then hacking
things such that "/usr/bin/pip" and "/usr/bin/virtalenv" remain
defaulted to python2 versions.
Documentation is added
Change-Id: Ibc6572b89e256d1f48b7fe7c672b8b9524dc704f
79d4113cbe