This run_test helper sets up a convention that allows
us to give really short tracebacks for errors, and
eventually we can have more control over running
individual tests. (The latter goal has some
complications, since we often intentionally leak
setup in tests.)
Our logic for editing failed messages is broken in various ways,
so we are removing the codepath for editing for now. We will
try to restore these features as part of #5841.
We remove the jquery dependency here and just search for strings
in the text. It turns out the test was leaking jquery into
message_edit, so now we explicitly stub jquery in message_edit.