tests: actually test something useful in test_edit for gists (Issue #376) Even though there was a test for editing gists, it did not catch the basic loading problem reported in issue #376. In fact, the test just loaded the edit page, but since no user was actually logged in, it just loaded the login screen. As a result, no real gist editing code was tested at all. Instead, explicitly check the redirection to a login screen, then proceed with logging in and check that the edit page can be loaded. Additionally, don't rely on the magic gist id '1' but create an actual gist first. Note: the test does not yet really edit a gist.