Apparently Python3 disallows casting numpy scalars into ints. Work around that.

gym/spaces/discrete.py

@@ -10,7 +10,13 @@ class Discrete(Space):
     def sample(self):
         return np.random.randint(self.n)
     def contains(self, x):
-        return isinstance(x, int) and x >= 0 and x < self.n
+        if isinstance(x, int):
+            as_int = x
+        elif x.dtype.kind in np.typecodes['AllInteger'] and x.shape == ():
+            as_int = int(x)
+        else:
+            return False
+        return as_int >= 0 and as_int < self.n
     def __repr__(self):
         return "Discrete(%d)" % self.n
     def __eq__(self, other):