Simplified get_user_id() and fixed possible python3 compatiblity issue.
Simplified get_user_id() and fixed possible python3 compatiblity issue.

Changed motivated by https://github.com/gitpython-developers/GitPython/pull/52

avinassh/GitPython,cdht/GitPython,gitpython-developers/GitPython,StyXman/GitPython,dpursehouse/GitPython,bwrsandman/GitPython,avinassh/GitPython,nvie/GitPython,breavo/GitPython,nvie/GitPython,breavo/GitPython,ghtdak/GitPython,gitpython-developers/gitpython,jeblair/GitPython,bwrsandman/GitPython,StyXman/GitPython,expobrain/GitPython,roidelapluie/GitPython,zsjohny/GitPython,manasdk/GitPython,cdht/GitPython,manasdk/GitPython,pengshp/GitPython,hvnsweeting/GitPython,ghtdak/GitPython,bwrsandman/GitPython,hvnsweeting/GitPython,roidelapluie/GitPython,dpursehouse/GitPython,h4ck3rm1k3/GitPython,zsjohny/GitPython,gitpython-developers/gitpython,beni55/GitPython,expobrain/GitPython,beni55/GitPython,pengshp/GitPython,pengshp/GitPython,avinassh/GitPython,StyXman/GitPython,h4ck3rm1k3/GitPython,cdht/GitPython,gitpython-developers/GitPython,zsjohny/GitPython,jeblair/GitPython