Fix return values of OAuth posts of mocks in test_associate.py.
Fix TestAccountElsewhere.test_bitbucket_oauth_url_percent_encodes_then.
Fix TestAccountElsewhere.test_github_oauth_url_not_susceptible_to_injection_attack.
Fix TestAccountElsewhere.test_opt_in_can_change_username.
Fix TestAccountElsewhere.test_twitter_oauth_url_percent_encodes_then.