Right now a test client can preserve the context for a little longer, so can exceptions. However there is no information if there is a context "on hold" on the stack which leads to the problem that if you continue to trigger exception you build up items on the stack in debug mode for nothing. There should always only be one context on the stack preserved and if another request comes in it should be removed.
This might also make the test client cleaner.
Context preserving is now part of Flask and not the test client. This…
… fixes #326