Show error if cannot get the authorization url

[perriman]

If there is no connection with twitter, this error is raised but not controlled

Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.6/cloudsn/ui/window.py", line 390, in providers_combo_changed_cb
    box = provider.get_account_data_widget(self.provider_content.account)
  File "/usr/lib/pymodules/python2.6/cloudsn/providers/twitterprovider.py", line 34, in get_account_data_widget
    return self.conf_widget.load()
  File "/usr/lib/pymodules/python2.6/cloudsn/providers/twitterprovider.py", line 55, in load
    auth_url = self.auth.get_authorization_url()
  File "/usr/lib/pymodules/python2.6/cloudsn/providers/tweepy/auth.py", line 103, in get_authorization_url
    raise TweepError(e)
cloudsn.providers.tweepy.error.TweepError: HTTP Error 403: Forbidden