handle the GITHUB_HOST='' case
handle the GITHUB_HOST='' case

santi81/oauthenticator,luisfdez/oauthenticator,zonca/oauthenticator,yuvipanda/mwoauthenticator,willjharmer/oauthenticator,jupyter/oauthenticator,willjharmer/oauthenticator,zonca/oauthenticator,yuvipanda/mwoauthenticator,luisfdez/oauthenticator,cmclaughlin/oauthenticator,maltevogl/oauthenticator,santi81/oauthenticator,jupyter/oauthenticator,jupyterhub/oauthenticator,NickolausDS/oauthenticator,enolfc/oauthenticator,cmclaughlin/oauthenticator,minrk/oauthenticator