Test ImportTasksView

Any feedback before I continue, @bobsilverberg?

My comment about these from previous PR: 
"I added some tests so y'all can see where I'm headed and maybe steer me in the right direction in terms of using Mock and such. I was in the middle of writing tests to see if the right template is used depending on which "stage" is posted. I think I need to pass in complete form data to get those tests to work."
Are there cases in which the view looks for the request in its own `self` scope? If not, and this mock request is only used by the tests to pass into methods, then I'd just define it as `self.request` as opposed to `self.view.request`.