Test both context_processor and app_context_processor functions.
Two context parameters are added into the context: one added to
the blueprint locally; another added to the app globally. The test
asserts the behaviors in both blueprint scope and the app scope.
The coverage for flask.blueprints is increased by 3%.
This test case registers an application-wise error handler from
a Blueprint. Verifies the error handler by aborting the flask app
from the application itself as well as from another registered
Blueprint.
