[rllib] Fix tune.run(Agent class) (#4630)

* update

* Update __init__.py

python/ray/rllib/tests/test_legacy.py

@@ -0,0 +1,15 @@
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+from ray.rllib.agents.ppo import PPOAgent
+from ray import tune
+import ray
+
+if __name__ == "__main__":
+    ray.init()
+    # Test legacy *Agent classes work (renamed to Trainer)
+    tune.run(
+        PPOAgent,
+        config={"env": "CartPole-v0"},
+        stop={"training_iteration": 2})

python/ray/rllib/utils/__init__.py

@@ -10,14 +10,18 @@ logger = logging.getLogger(__name__)
 
 
 def renamed_class(cls):
+    """Helper class for renaming Agent => Trainer with a warning."""
+
     class DeprecationWrapper(cls):
-        def __init__(self, *args, **kwargs):
+        def __init__(self, config=None, env=None, logger_creator=None):
             old_name = cls.__name__.replace("Trainer", "Agent")
             new_name = cls.__name__
             logger.warn("DeprecationWarning: {} has been renamed to {}. ".
                         format(old_name, new_name) +
                         "This will raise an error in the future.")
-            cls.__init__(self, *args, **kwargs)
+            cls.__init__(self, config, env, logger_creator)
+
+    DeprecationWrapper.__name__ = cls.__name__
 
     return DeprecationWrapper