MigrationsTestCase is intentionally omitted from this, since migrations
tests are different in their nature and so whatever setUp()
ZulipTestCase may do in the future, MigrationsTestCase may not
necessarily want to replicate.
Previously, this function executed the same test as
test_bots.py/test_create_embedded_bot_with_incorrect_service_name().
Now, instead of testing to add an embedded bot with an incorrect service
name, we test messaging an embedded bot with an incorrect service
name.
External bots may call bot_handler.quit() when
they wish to terminate, e.g. due to a misconfiguration.
Currently, embedded bots ignore calls to quit(), even
though they signal a problem. This commit does the first
step in handling quit() calls by logging a warning.