alternative for reading python requirements

I know very little python so this may be completely wrong, but this fixes #120 on my CentOS 6.3 machine.  

My guess is the "-r base.txt" is what is causing the issue although I cannot find any documentation as to what the -r (or -x and -e flags for that matter) does, but it appears to also load requirements from a second file as well.  Achieving that through code rather than the -r flag.