Fix failing windows tests

[jhamrick]

Fixes #479, yay! 🎉

[willingc]

@jhamrick Any reason not to merge this now?

[jhamrick]

Because the tests still aren't passing on Jenkins :-(

[willingc]

Perhaps merge this and then work on the Windows and Jenkins issue independently.

[jhamrick]

The windows tests are finally all passing for reals, hurray! Merging as soon as travis is happy 🎉

[willingc]

oooh... nicely done @jhamrick

[willingc]

So did you set the cookies-file to dev/null to just disable it

[jhamrick]

Yes. I still don't exactly know why it's a problem with the nbextensions tests and not the formgrader tests (maybe just a race condition?) but it seems to work now so I'm going to leave it at that :-)

[willingc]

Or perhaps it's just nbextensions... either way your plan to just go with seems good. How's UK?

[jhamrick]

Yeah, I figure especially since it's just something in the test logic rather than nbgrader itself it doesn't matter too much as long as the tests pass.

The UK is awesome! London is such a cool city :-) How's California?

[willingc]

California is hot. Enjoying working with the summer interns who you will meet at SciPy. See you there 😄

[jhamrick]

Yes, looking forward to it! :-)