Provide integration test_hooks to be used in gate job

Using scripts inside horizon repo in test hooks we could not bother
infra folks each time when we need to do some change to test job.

The second part of the proposed change is to run these scripts at gate,
see https://review.openstack.org/#/c/263457/

Related-Bug: #1526791
Change-Id: Ic2d60df846e876530662046d75c3e56e7841ba30

doc/source/topics/testing.rst

@@ -301,7 +301,16 @@ which also contains instructions on how to run the tests. To make integration
 tests more understandable and maintainable, the Page Object pattern is used
 throughout them.
 
+Horizon repository also provides two shell `scripts`_, which are executed in
+pre_test_hook and post_test_hook respectively. Pre hook is generally used for
+modifying test environment, while post hook is used for running actual
+integration tests with tox and collecting test artifacts. Thanks to the
+incorporating all modifications to tests into Horizon repository, one can alter
+both tests and test environment and see the immediate results in Jenkins job
+output.
+
 .. _here: https://github.com/openstack/horizon/tree/master/openstack_dashboard/test/integration_tests
+.. _scripts: https://github.com/openstack/horizon/tree/master/tools/gate/integration
 
 Page Object pattern
 -------------------

tools/gate/integration/post_test_hook.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+# This script will be executed inside post_test_hook function in devstack gate
+
+cd /opt/stack/new/horizon
+sudo -H -u stack tox -e py27integration
+retval=$?
+if [ -d openstack_dashboard/test/integration_tests/integration_tests_screenshots/ ]; then
+  cp -r openstack_dashboard/test/integration_tests/integration_tests_screenshots/ /home/jenkins/workspace/gate-horizon-dsvm-integration/
+fi
+exit $retval
+

tools/gate/integration/pre_test_hook.sh

@@ -0,0 +1,4 @@
+#!/bin/bash
+
+# This script will be executed inside pre_test_hook function in devstack gate
+