Fix flake8 issue.
Fix flake8 issue.

It's new in the latest version of flake - thanks travis for letting me know.

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