authtwitter: throw UserAborted error when the user cancels authentication.
authtwitter: throw UserAborted error when the user cancels authentication.

Thanks to Andjelko Horvat for implementing this.

git-svn-id: a243b28a2a52d65555a829a95c8c333076d39ae1@2775 44740490-163a-0410-bde0-09ae8108e29a

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