Invalid upstream response (201)

[jomo]

This image doesn't show up because the server returns a 201:

![201 test](https://img-any-status.herokuapp.com/201)

201 is typical for POST or PUT requests, but I can't find anything that states it would be invalid as response to GET.

I think #77 should have fixed that and can't actually find the code for the error message in the sources, but I thought I'd report here since it seems to be related to camo.

[jomo]

camo forwards the status code it receives, see here. Possibly it's whatever GitHub places in front of it? Google doesn't return anything meaningful for that error message, either.