* Hide "Test Code" button after we check the problem
* Only set the state of the problem to 'queued' if we have successfully
queued the problem
* Unit tests for bugs and new functionality

Pylint fixes

Add tests for unicode and escaped HTML characters

for Matlab inputs

context for scripts to access.
This was removed accidentally during an earlier refactoring,
which caused customresponse to raise an exception for chem problems.
Unit tests verify the changes

comparison of correctness in multiple choice.

Multiple choice code is scattered and sometimes sends a list of
choices for the value, and sometimes a single string. We used to use
"in" which scarily handled both cases (list or substring search),
but that caused a bug when you had two choices like choice_1 and
choice10. Moving to == caused us to break when lists were sent to
us. So this ugly code is extra paranoid and checks both possibilities.

This really needs a better cleanup.

is set to an integer (and correctly saved) instead of a tuple.

* Removed duplicate traceback log message
* Now provide string, not Exception, as second tuple item to raise

Added tests for SchematicResponse error handling

causing a 500 error.

When XModule raises a ProcessingError during an AJAX request,
this module_render now returns a 404 to further reduce number of 500
responses.

which is the only other response type to use StudentInputError.

if the user is a staff member.
Otherwise, it displays just the exception message.

was causing 500 errors. Add test to verify that this won't
happen again.