make the tests that expect uncatchable exceptions from a callback test for them in a roundabout way (catching and parsing stderr)
make the tests that expect uncatchable exceptions from a callback test
for them in a roundabout way (catching and parsing stderr)

keeps test output clean.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator