Fix Unicode Problems in req_install.py

I encountered this error while using get-pip.py version, though I decided to fix this in develop branch.

I also have problems in logger, but that is [reported 7 months ago](https://github.com/pypa/pip/issues/1137).
[The fix](https://github.com/pypa/pip/issues/1137#issuecomment-23613766) is also working for me.