run-tempest role: new tempest_test_regex variable

Specify a regular expression to filter the tests.

Change-Id: I44911c6bd6ede68c3376c8a6b42700310dce7a06

roles/run-tempest/README.rst

@@ -12,6 +12,13 @@ Run Tempest
 
    The number of parallel test processes.
 
+.. zuul:rolevar:: tempest_test_regex
+   :default: ''
+
+   A regular expression used to select the tests.
+   It works only when used with some specific tox environments
+   ('all', 'all-plugin'.)
+
 .. zuul:rolevar:: tox_venvlist
    :default: smoke
 

roles/run-tempest/defaults/main.yaml

@@ -1,2 +1,3 @@
 devstack_base_dir: /opt/stack
+tempest_test_regex: ''
 tox_venvlist: smoke

roles/run-tempest/tasks/main.yaml

@@ -21,7 +21,7 @@
   when: num_cores|int > 3
 
 - name: Run Tempest
-  command: tox -e {{tox_venvlist}} -- --concurrency={{tempest_concurrency|default(default_concurrency)}}
+  command: tox -e {{tox_venvlist}} -- {{tempest_test_regex|quote}} --concurrency={{tempest_concurrency|default(default_concurrency)}}
   args:
     chdir: "{{devstack_base_dir}}/tempest"
   become: true