git-pw: Enable test-state filter on list subcommand

This new filter allows to filter lists by test states; some examples:

$ git pw list --test-state success

NOTES:
* The test state queried correspond to the last revision
* If there are many tests done against a particular series/revision (having
  different name each), the test state 'summary' would be the one having
  more priority, currently defined as 'pending', 'success', 'warning' and
  'failure', the former has the lowest priority and the latter the highest.

v2: A few minor tweaks (Damien)
    #154

Signed-off-by: Leonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com>

git-pw/git-pw

@@ -162,6 +162,23 @@ class User(object):
         self.password = password
 
 
+class TestState(object):
+    PENDING = 0
+    SUCCESS = 1
+    WARNING = 2
+    FAILURE = 3
+    CHOICES = (
+        (PENDING, 'pending'),
+        (SUCCESS, 'success'),
+        (WARNING, 'warning'),
+        (FAILURE, 'failure'),
+    )
+
+    @classmethod
+    def choices(cls):
+        return [s for _, s in cls.CHOICES]
+
+
 class RestObject(object):
 
     def __init__(self, patchwork):
@@ -635,6 +652,8 @@ class GitPatchwork(object):
         elif self.cmd.updated_since:
             params['ordering'] = 'last_updated'
             params['updated_since'] = self.cmd.updated_since
+        elif self.cmd.test_state:
+            params['test_state'] = self.cmd.test_state
 
         series_list = []
         try:
@@ -913,6 +932,10 @@ if __name__ == '__main__':
         type=str, choices=Series.FIELDS, default=default_series_fields,
         help='list of fields to display')
 
+    list_parser.add_argument('--test-state', metavar='test_state',
+         type=str, choices=TestState.choices(),
+         help='retrieve series with a particular test state')
+
     git_pw = GitPatchwork()
     parser.parse_args(namespace=git_pw.cmd)