[rllib] Fix PyTorch initialization (#1961)

* Fix typo

* Fix A3C PyTorch agent initialization

`registry` needs to be passed as an argument or else the `super` init will
fail.

python/ray/rllib/a3c/shared_torch_policy.py

@@ -17,9 +17,9 @@ class SharedTorchPolicy(TorchPolicy):
     other_output = ["vf_preds"]
     is_recurrent = False
 
-    def __init__(self, ob_space, ac_space, config, **kwargs):
+    def __init__(self, registry, ob_space, ac_space, config, **kwargs):
         super(SharedTorchPolicy, self).__init__(
-            ob_space, ac_space, config, **kwargs)
+            registry, ob_space, ac_space, config, **kwargs)
 
     def _setup_graph(self, ob_space, ac_space):
         _, self.logit_dim = ModelCatalog.get_action_dist(ac_space)

python/ray/tune/registry.py

@@ -23,7 +23,7 @@ def register_trainable(name, trainable):
 
     Args:
         name (str): Name to register.
-        trainable (obj): Function or tune.Trainable clsas. Functions must
+        trainable (obj): Function or tune.Trainable class. Functions must
             take (config, status_reporter) as arguments and will be
             automatically converted into a class during registration.
     """