make DQN runnable

PYTHONPATH=/paddle/build/python python train.py --rom ./rom_files/pong.bin  --alg DuelingDQN

fluid/DeepQNetwork/DuelingDQN_agent.py

@@ -158,7 +158,8 @@ class DuelingDQNModel(object):
             for i, var in enumerate(policy_vars):
                 sync_op = fluid.layers.assign(policy_vars[i], target_vars[i])
                 sync_ops.append(sync_op)
-        sync_program = sync_program.prune(sync_ops)
+        # The prune API is deprecated, please don't use it any more.
+        sync_program = sync_program._prune(sync_ops)
         return sync_program
 
     def act(self, state, train_or_test):

fluid/DeepQNetwork/atari.py

@@ -9,7 +9,7 @@ import gym
 from gym import spaces
 from gym.envs.atari.atari_env import ACTION_MEANING
 
-from ale_python_interface import ALEInterface
+from atari_py import ALEInterface
 
 __all__ = ['AtariPlayer']