Cleanup error messages on failure

When test_server_commands_main_help() fails it dumps a ton of
unformatted text on an exception message. This commit attempts to clean
it up to make it easier to read.

Change-Id: I793e6337728a22302a5a87938dbec60d7f2320d8

Author: mtreinish

openstackclient/tests/functional/common/test_help.py

@@ -60,8 +60,12 @@ def test_server_commands_main_help(self):
         """Check server commands in main help message."""
         raw_output = self.openstack('help')
         for command, description in self.SERVER_COMMANDS:
-            self.assertIn(command, raw_output)
-            self.assertIn(description, raw_output)
+            msg = 'Command: %s not found in help output:\n%s' % (
+                command, raw_output)
+            self.assertIn(command, raw_output, msg)
+            msg = 'Description: %s not found in help output:\n%s' % (
+                description, raw_output)
+            self.assertIn(description, raw_output, msg)
 
     def test_server_only_help(self):
         """Check list of server-related commands only."""