Update koji/__init__.py
    
    with old configuration/obsoleted koji authetication, we have variables like ~/.rpmfusion.cert , It would be nice that koji expand ~ to user home .

    As workaround we send variable already expanded ( https://github.com/rpmfusion-infra/rfpkg/commit/fc2a94d1135bace0a9e5888ffb3f3a35d95e0cf8 )