Ataki/gridfs

@stvstnfrd to review commit
Having not seen this UI yet, would it make sense to still show the
filename so that the user knows which file caused the error?

I didn't mention this before, but with changes affecting UI, it often
helps to include relevant screenshots in your PR. I still plan on
checking this out locally, but it helps to give a preliminary view. It
is also beneficial when being reviewed by non-technical personel (think
Product and CourseOps) or really anyone that won't check the code out in
a devstack).