I wrote about why this was a bad idea at: http://notes.pault.ag/debian-python/
If you want a clear failure mode - if this installs requests globally, think about the chaos if you're on Debian stable, with 0.12.1, before the API break - after a pip install, you may end up with all the software on your system broken.
When this happens, please don't file bugs with Debian. Thanks.