We happened to be building a new build server today, and one of the steps in the process is to install packages.  We download all of the packages to local disk in one step (pip install --download ${packages}), then install them in the next step (pip install --no-index --find-links ${packages}).  Thing is, while pytz downloaded with the install command, it would not install from the downloaded package.

pip is now 1.4, which rejects the 2013b pytz release that was downloaded in the step before as being a pre-release.  You can get around it with a pytz==2013b in your requirements declaration, but that's a bit annoying, as it now needs to be manually updated when there's a new release.

I believe the pytz names are based on the underlying Olson database release names, but in Python release numbering 2013b is a beta/prerelease of 2013, not the second release in the 2013 year.  I guess maybe it's pytz that should re-number?  Anyway, in the meantime, beware the pip update...