We build RPMs with (mock)[http://fedoraproject.org/wiki/Projects/Mock] which installs all build requirements from our YUM repos. Using pip or other means to pull data from the Internet is not supported in that environment.

I prefer us to stay a bit more conservative in the choice of our tools than to increase the amount of extra libs to maintain. This also makes it easier for others to adopt our code as they can use it with the standard libs provided by RHEL and EPEL.