Added warnings to command module

Generate warnings when users are shelling out to commands
rather than using modules

Can be turned off on a per-action line with the documented
warn=False flag. Can be turned off globally using
command_warnings = False in ansible config file.

Print out warnings using the standard playbook callbacks.

Created some additional tests in TestRunner.test_command
and also a demonstration playbook.

lib/ansible/callbacks.py

@@ -535,6 +535,9 @@ class PlaybookRunnerCallbacks(DefaultRunnerCallbacks):
                 display(msg, color='green', runner=self.runner)
             else:
                 display(msg, color='yellow', runner=self.runner)
+        if constants.COMMAND_WARNINGS and 'warnings' in host_result2 and host_result2['warnings']:
+            for warning in host_result2['warnings']:
+                display("warn: %s" % warning, color='purple', runner=self.runner)
         super(PlaybookRunnerCallbacks, self).on_ok(host, host_result)
 
     def on_skipped(self, host, item=None):

lib/ansible/constants.py

@@ -170,6 +170,7 @@ HOST_KEY_CHECKING              = get_config(p, DEFAULTS, 'host_key_checking',  '
 SYSTEM_WARNINGS                = get_config(p, DEFAULTS, 'system_warnings', 'ANSIBLE_SYSTEM_WARNINGS', True, boolean=True)
 DEPRECATION_WARNINGS           = get_config(p, DEFAULTS, 'deprecation_warnings', 'ANSIBLE_DEPRECATION_WARNINGS', True, boolean=True)
 DEFAULT_CALLABLE_WHITELIST     = get_config(p, DEFAULTS, 'callable_whitelist', 'ANSIBLE_CALLABLE_WHITELIST', [], islist=True)
+COMMAND_WARNINGS               = get_config(p, DEFAULTS, 'command_warnings', 'ANSIBLE_COMMAND_WARNINGS', True, boolean=True)
 
 # CONNECTION RELATED
 ANSIBLE_SSH_ARGS               = get_config(p, 'ssh_connection', 'ssh_args', 'ANSIBLE_SSH_ARGS', None)