pip search incorrectly shows release candidates as latest version

[cdeil]

I noticed that pip search astropy-helpers currently incorrectly shows 0.4rc3 as the latest version, where it should show 0.4 as the latest version:

$ pip search astropy-helpers
astropy-helpers           - Utilities for building and installing Astropy, Astropy affiliated packages, and their respective documentation.
  INSTALLED: 0.4
  LATEST:    0.4rc3

I think this is a bug in the pip.commands.search.compare_versions implementation (I have pip version 1.5.6 with Python 2.7), because according to PEP-0386 one should get "0.4rc3" < "0.4", no?

>>> from pip.commands import search
>>> search.compare_versions('0.4', '0.3')
1
>>> search.compare_versions('0.4', '0.4rc3')
-1

[embray]

ISTM this could probably be addressed as part of #1894, though search.compare_versions would have to be either removed, or rewritten to use the new version scheme instead of the legacy version comparison.

[xavfernandez]

pip is just a client of PyPI search XMLRPC API.
So this was a bug on PyPI side instead of pip. cf #3788 for a similar issue