Pin sphinx to <1.2

There is a bug in sphinx 1.2 that breaks doc builds.

See requirements commit 0e8862e958813a031fe7398440e8a3866b42a8e4
for details.

copied from https://review.openstack.org/#/c/61209/
Related-Bug: 1259511

Change-Id: Iea8ef70dd46faa1ad8f52c9b772dd7fa16902316
Have tox install via setup.py develop

tox 1.6 was released, which means that we can now take advantage of
the feature we added to it - which is using setup.py develop to
install the code into the virtualenv. The logic was taken from
run_tests.sh - so the performance issues around using tox vs. using
install_venv should now be gone.

Additionally, override the tox pip install command to avoid using
the "--pre" option which is the default in tox. "--pre" means
"Include pre-release and development versions." By default, pip will
only install stable versions of software, and that is the behavior
we want.

Change-Id: Ida5e440d1bdb9f8e9031277ea53a02d2ef171438
Co-Authored-By: Monty Taylor <mordred@inaugust.com>
Don't raise MySQL 2013 'Lost connection' errors

Closes-bug: #1276510

Although this code error is part of the `ping_listener` tests, it was
missing from the list of known - and ignored - connection errors.

The code error 2013 refers to a connection lost during a query, see:
https://dev.mysql.com/doc/refman/5.0/en/error-messages-client.html#error_cr_server_lost

Without this error code, the session won't try to reconnect to mysql,
which makes `max_retries` useless.

Change-Id: If2667cf83ac656666ffe00aa90e3454516b080db
(cherry picked from commit b4f72b2987d53bb434e3a833f06d70a2167f5efc)