Redirects broken with latest Flask release 1.0.3

[RookieRick]

Appears to be due to pallets/flask#2986

At first glance it looks to me like we're no longer getting an "error" on redirect (and we end up with default mimetype of text/html in the 301 response).

Could use another set of eyes (particularly people more intimately familiar with the internals of Flask than I ;) ) to help understand what's happening and how we can cleanly address. To reproduce, simply update Flask from 1.0.2 to 1.0.3 and run our unit tests.

[RookieRick]

OK after looking at that referenced Flask PR seems there's a suggested workaround there; will give that a shot (which I suspect means we'll have three separate conditions we test for when setting MOVED_PERMANENTLY_ERROR and PERMANENT_REDIRECT_ERROR)

[RookieRick]

...and after still more inspection and reflection, I'm torn.. The suggested workaround that may be applicable is to override Flask's handle_http_exception -- while I can see a way that could work (we could insert a check for 301/308 specifically before passing through to default functionality there), it feels awfully dirty to me, and perhaps something better left to our users if they indeed require it.

Ultimately, the behavior of Flask has changed from raising an exception for redirects to simply returning them as a result. I'm not sure I agree with that (especially for a point-release), but it seems to be characterized as an unintentional behavior in 1.0, so it's possible our best (or at least most "correct") course of action here is to accept it as-is, and update our test to expect text/html in the case of a redirect.

I'll tinker with it some more and see if I can come up with any better ideas than that; other suggestions most definitely welcome.

[RookieRick]

Addressing with PR #97 - changed only the test as the underlying Flask behavior has changed and I don't see a clean way to address it in Rebar.