Bring cloudpickle inside the repository. (#1445)

* Bring cloudpickle version 0.5.2 inside the repo.

* Use internal copy of cloudpickle everywhere.

* Fix linting.

* Import ordering.

* Change __init__.py.

* Set pickler in serialization context.

* Don't check ray location.

python/ray/worker.py

@@ -3,7 +3,6 @@ from __future__ import division
 from __future__ import print_function
 
 import atexit
-import cloudpickle as pickle
 import collections
 import colorama
 import copy
@@ -22,6 +21,7 @@ import traceback
 # Ray modules
 import pyarrow
 import pyarrow.plasma as plasma
+import ray.cloudpickle as pickle
 import ray.experimental.state as state
 import ray.serialization as serialization
 import ray.services as services
@@ -1040,6 +1040,9 @@ def _initialize_serialization(worker=global_worker):
     serialize several exception classes that we define for error handling.
     """
     worker.serialization_context = pyarrow.SerializationContext()
+    # Tell the serialization context to use the cloudpickle version that we
+    # ship with Ray.
+    worker.serialization_context.set_pickle(pickle.dumps, pickle.loads)
     pyarrow.register_default_serialization_handlers(
         worker.serialization_context)