cli: add messages to assertTrue

1) Unify assertion of 'usage: service-name' from
   {cinder, glance, keystone, neutron} help tests
   into assertFirstLineStartsWith method, which provides
   more usefull failure message.
2) Add failure message to assertTrue in keystone-catalog
   test.

Change-Id: I3abba1d9509bee649aa1675beee4153341b1e170

tempest/cli/__init__.py

@@ -134,6 +134,11 @@ class ClientTestBase(tempest.test.BaseTestCase):
             for field in field_names:
                 self.assertIn(field, item)
 
+    def assertFirstLineStartsWith(self, lines, beginning):
+        self.assertTrue(lines[0].startswith(beginning),
+                        msg=('Beginning of first line has invalid content: %s'
+                             % lines[:3]))
+
 
 class CommandFailed(subprocess.CalledProcessError):
     # adds output attribute for python2.6

tempest/cli/simple_read_only/test_cinder.py

@@ -87,7 +87,7 @@ class SimpleReadOnlyCinderClientTest(tempest.cli.ClientTestBase):
     def test_admin_help(self):
         help_text = self.cinder('help')
         lines = help_text.split('\n')
-        self.assertTrue(lines[0].startswith('usage: cinder'))
+        self.assertFirstLineStartsWith(lines, 'usage: cinder')
 
         commands = []
         cmds_start = lines.index('Positional arguments:')

tempest/cli/simple_read_only/test_glance.py

@@ -48,7 +48,7 @@ class SimpleReadOnlyGlanceClientTest(tempest.cli.ClientTestBase):
     def test_glance_help(self):
         help_text = self.glance('help')
         lines = help_text.split('\n')
-        self.assertTrue(lines[0].startswith('usage: glance'))
+        self.assertFirstLineStartsWith(lines, 'usage: glance')
 
         commands = []
         cmds_start = lines.index('Positional arguments:')

tempest/cli/simple_read_only/test_keystone.py

@@ -46,7 +46,9 @@ class SimpleReadOnlyKeystoneClientTest(tempest.cli.ClientTestBase):
         out = self.keystone('catalog')
         catalog = self.parser.details_multiple(out, with_label=True)
         for svc in catalog:
-            self.assertTrue(svc['__label'].startswith('Service:'))
+            self.assertTrue(svc['__label'].startswith('Service:'),
+                            msg=('Invalid beginning of service block: %s' %
+                                 svc['__label']))
 
     def test_admin_endpoint_list(self):
         out = self.keystone('endpoint-list')
@@ -94,7 +96,7 @@ class SimpleReadOnlyKeystoneClientTest(tempest.cli.ClientTestBase):
     def test_admin_help(self):
         help_text = self.keystone('help')
         lines = help_text.split('\n')
-        self.assertTrue(lines[0].startswith('usage: keystone'))
+        self.assertFirstLineStartsWith(lines, 'usage: keystone')
 
         commands = []
         cmds_start = lines.index('Positional arguments:')

tempest/cli/simple_read_only/test_neutron.py

@@ -92,7 +92,7 @@ class SimpleReadOnlyNeutronClientTest(tempest.cli.ClientTestBase):
     def test_neutron_help(self):
         help_text = self.neutron('help')
         lines = help_text.split('\n')
-        self.assertTrue(lines[0].startswith('usage: neutron'))
+        self.assertFirstLineStartsWith(lines, 'usage: neutron')
 
         commands = []
         cmds_start = lines.index('Commands for API v2.0:')