Add tools/tempest_coverage.py script.

This adds support for testing tempest's coverage on nova.
tools/tempest_coverage.py will enable coverage reporting in
nova to be started and stopped. It also performs coverage report
generation.

When it is enabled from run_tests with '-c' or '--nova_coverage'
a single text report file will be generated per nova service.

Implements: blueprint tempest-coverage-reporting
Change-Id: I00a52fb013c5a7a66a2317dbd5359a22d35bdb29
Signed-off-by: Matthew Treinish <treinish@linux.vnet.ibm.com>
diff --git a/tox.ini b/tox.ini
index 2d8e627..991842c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,6 +13,11 @@
        -r{toxinidir}/tools/test-requires
 commands = nosetests {posargs}
 
+[testenv:coverage]
+commands = python tools/tempest_coverage.py -c start --combine
+           nosetests {posargs}
+           python tools/tempest_coverage.py -c report --html
+
 [testenv:pep8]
 deps = pep8==1.3.3
 commands = python tools/hacking.py --ignore=N4,E122,E125,E126 --repeat --show-source --exclude=.venv,.tox,dist,doc,openstack,*egg .