tox runs single threaded and can't be overridden

[John Griffith]

I noticed that I couldn't get tox to run more than a single thread; turns out that we are setting "--no-parallel" in the pretty_tox.sh
file. Removing that makes the default run such that it consumes as many threads as you have available.

This is great and speeds things up significantly; one problem however is that once you get above around 6 parallel test processes things start to get a bit unstable. It's possibly an issue with some of our GIANT test classes that share some fakes/mocks but not sure. Could be we just can't run that many jobs in parallel.

In the meantime, I think lifting the single process limit is useful, and just like we did with run_tests you can specify concurrency if needed:
"tox -epy27 -- --concurrency=6"

NOTE: 6 seems to be the threshold for now.

[John Griffith (john-griffith)]

Note, bug regarding stability here: https://bugs.launchpad.net/cinder/+bug/1459854

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/186586

[OpenStack Infra (hudson-openstack)]

Change abandoned by John Griffith (<email address hidden>) on branch: master
Review: https://review.openstack.org/186586
Reason: this will hopefully be made obsolete with the move to using os-testr and removing pretty_tox altogether.

https://review.openstack.org/#/c/186879/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/186879
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=68b4aad405c019d660b86f62617394e8b170c2ea
Submitter: Jenkins
Branch: master

commit 68b4aad405c019d660b86f62617394e8b170c2ea
Author: John Griffith <email address hidden>
Date: Fri May 29 13:02:13 2015 -0600

    Remove pretty_tox and use ostestr

    This patch dumps pretty_tox.sh and gets Cinder on board
    with using ostestr. We're setting a concurrency value
    of 6 (instances in the gate are 6 VCPU's), and things
    seem to be stable at this value.

    For folks running on 'smaller' system, it's still possible
    to run in parallell; > ncpu's but if there are problems you
    can still specify concurrency in your tox argument. Tox will
    take the last occurence of the conncurrency argument; so for
    example if you specify "tox -epy27 -- --concurrency=4" the
    interpretted value for concurrency in the run will be 4.

    Closes-Bug: #1459852

    Change-Id: Iae12b42e915da22c863781015512df4f30aa95ca