[Python-modules-team] Bug#771794: Bug#771794: pip silently removes/updates system provided python packages

[Piotr Ożarowski]

IMO we should patch pip to *not* touch (install, upgrade, uninstall,
etc.) anything in /usr directory (or /) except /usr/local. Our Python
interpreter already installs to /usr/local and so should pip.

This way:
 * pip doesn't need to figure out which file can be touched,
 * we can detect cause of problems just by looking at traceback
   (right now the very first thing I do once someone sends me a
   traceback is to look for .egg files in there (thank you ez_install!);
   with pip installing/overwriting files in /usr instead of /usr/local
   it's not that easy, not to mention that it will be a lot harder to
   fix it after such "install")
 * we'll be able to easily prove to our users that we're not insane
   and we did test our stuff ("please rename
   /usr/local/pythonX.Y/dist-packages to something else for few minutes
   and try again")