remove double-wrap warning (#1061)

* remove double-wrap warning

* remove double-wrap tests

gym/core.py

@@ -244,22 +244,11 @@ class Wrapper(Env):
         self.observation_space = self.env.observation_space
         self.reward_range = self.env.reward_range
         self.metadata = self.env.metadata
-        self._warn_double_wrap()
 
     @classmethod
     def class_name(cls):
         return cls.__name__
 
-    def _warn_double_wrap(self):
-        env = self.env
-        while True:
-            if isinstance(env, Wrapper):
-                if env.class_name() == self.class_name():
-                    raise error.DoubleWrapperError("Attempted to double wrap with Wrapper: {}".format(self.__class__.__name__))
-                env = env.env
-            else:
-                break
-
     def step(self, action):
         if hasattr(self, "_step"):
             deprecated_warn_once("%s doesn't implement 'step' method, but it implements deprecated '_step' method." % type(self))

gym/wrappers/tests/test_wrappers.py

@@ -1,21 +0,0 @@
-import gym
-from gym import error
-from gym import wrappers
-import tempfile
-import shutil
-
-
-def test_no_double_wrapping():
-    temp = tempfile.mkdtemp()
-    try:
-        env = gym.make("FrozenLake-v0")
-        env = wrappers.Monitor(env, temp)
-        try:
-            env = wrappers.Monitor(env, temp)
-        except error.DoubleWrapperError:
-            pass
-        else:
-            assert False, "Should not allow double wrapping"
-        env.close()
-    finally:
-        shutil.rmtree(temp)