Improve help text for extra-vars requiring @ for filename

lib/ansible/cli/__init__.py

@@ -308,7 +308,7 @@ class CLI(with_metaclass(ABCMeta, object)):
                 action="callback", callback=CLI.expand_tilde, type=str)
         if runtask_opts:
             parser.add_option('-e', '--extra-vars', dest="extra_vars", action="append",
-                help="set additional variables as key=value or YAML/JSON", default=[])
+                help="set additional variables as key=value or YAML/JSON, if filename prepend with @", default=[])
 
         if fork_opts:
             parser.add_option('-f','--forks', dest='forks', default=C.DEFAULT_FORKS, type='int',

lib/ansible/modules/web_infrastructure/ansible_tower/tower_job_launch.py

@@ -54,7 +54,7 @@ options:
       default: null
     extra_vars:
       description:
-        - Extra_vars to use for the job_template. Use '@' for a file.
+        - Extra_vars to use for the job_template. Prepend '@' if a file.
       default: null
     limit:
       description: