Bug 1030972 - Import tasks from Bugzilla

@bobsilverberg @Osmose r?
Yeah, I was on the fence with this one. Users of the view won't be able to do anything to address this kind of error except tell maintainers about it, so I thought it might be best to just log it. If I bubble it up instead, how about a message like "Sorry. we cannot retrieve any data from [source] at this time. Please report this to the One and Done team."?