Bug 1030972 - Import tasks from Bugzilla

@bobsilverberg @Osmose r?
I suggest to keep the asserts there to make assumptions about this view obvious and to act as a complement to unit tests. The asserts really should never fail, if you look at the possible states for this view. If one of these asserts fails, something fundamentally bizarre has happened and it's reasonable to show a 500 error to the user.