Fun situation: I cannot use my google account (email address) in bugzilla.mozilla.org. The site tells me that my email address is already in use but does not provide the option to log in with another email address or with github.
> The site tells me that my email address is already in use
This means you already have an account on bugzilla.mozilla.org; you can use the "Forgot Password" link in the header to recover that account's password.
I have an account on connect.mozilla.org, which uses google to authenticate me. In Bugzilla, I can only add a new (different) email address or use github to authenticate. Using my google email address I get the error message that my email address is already in use. No option to chose google as a authenticating service.