Learn.py now takes a config file as a required arg.

mlagents/learn.py

     logger = logging.getLogger("mlagents.learn")
     _USAGE = '''
     Usage:
-      learn (<env>) [options]
+      learn (<trainer-config-path>) [<env>] [options]
       learn [options]
       learn --help
 
     lesson = int(options['--lesson'])
     fast_simulation = not bool(options['--slow'])
     no_graphics = options['--no-graphics']
-
-    # Constants
-    # Assumption that this yaml is present in same dir as this file
-    base_path = os.path.dirname(__file__)
-    TRAINER_CONFIG_PATH = os.path.abspath(os.path.join(base_path, "trainer_config.yaml"))
+    trainer_config_path = options['<trainer-config-path>']
-                               docker_target_name, TRAINER_CONFIG_PATH, no_graphics)
+                               docker_target_name, trainer_config_path, no_graphics)
         tc.start_learning()