fixes related to new gym and new flake8

baselines/common/distributions.py

@@ -75,7 +75,8 @@ class CategoricalPdType(PdType):
 
 class MultiCategoricalPdType(PdType):
     def __init__(self, nvec):
-        self.ncats = nvec
+        self.ncats = nvec.astype('int32')
+        assert (self.ncats > 0).all()
     def pdclass(self):
         return MultiCategoricalPd
     def pdfromflat(self, flat):

baselines/her/ddpg.py

@@ -410,7 +410,7 @@ class DDPG(object):
         logs += [('stats_g/mean', np.mean(self.sess.run([self.g_stats.mean])))]
         logs += [('stats_g/std', np.mean(self.sess.run([self.g_stats.std])))]
 
-        if prefix is not '' and not prefix.endswith('/'):
+        if prefix != '' and not prefix.endswith('/'):
             return [(prefix + '/' + key, val) for key, val in logs]
         else:
             return logs

baselines/her/rollout.py

@@ -163,7 +163,7 @@ class RolloutWorker:
             logs += [('mean_Q', np.mean(self.Q_history))]
         logs += [('episode', self.n_episodes)]
 
-        if prefix is not '' and not prefix.endswith('/'):
+        if prefix != '' and not prefix.endswith('/'):
             return [(prefix + '/' + key, val) for key, val in logs]
         else:
             return logs