pkey: fix comparison with None

A bug introduced by 54da670 (added in v2.6.4)

paramiko/pkey.py

@@ -114,7 +114,8 @@ def __str__(self):
 
     def __cmp__(self, other):
         # python-2 only, same purpose as __eq__()
-        return cmp(self.asbytes(), other.asbytes())  # noqa
+        other_asbytes = other.asbytes() if isinstance(other, PKey) else b""
+        return cmp(self.asbytes(), other_asbytes)  # noqa
 
     def __eq__(self, other):
         """
@@ -125,7 +126,7 @@ def __eq__(self, other):
 
         :param .PKey other: key to compare to.
         """
-        return self.asbytes() == other.asbytes()
+        return isinstance(other, PKey) and self.asbytes() == other.asbytes()
 
     def get_name(self):
         """

tests/test_pkey.py

@@ -161,6 +161,9 @@ def test_2_load_rsa(self):
         key2 = RSAKey.from_private_key(s)
         self.assertEqual(key, key2)
 
+        # ensure comparison does not raise exception
+        assert key != None  # noqa: E711
+
     def test_3_load_rsa_password(self):
         key = RSAKey.from_private_key_file(_support('test_rsa_password.key'), 'television')
         self.assertEqual('ssh-rsa', key.get_name())
@@ -186,6 +189,9 @@ def test_4_load_dss(self):
         key2 = DSSKey.from_private_key(s)
         self.assertEqual(key, key2)
 
+        # ensure comparison does not raise exception
+        assert key != None  # noqa: E711
+
     def test_5_load_dss_password(self):
         key = DSSKey.from_private_key_file(_support('test_dss_password.key'), 'television')
         self.assertEqual('ssh-dss', key.get_name())
@@ -298,6 +304,9 @@ def test_10_load_ecdsa_256(self):
         key2 = ECDSAKey.from_private_key(s)
         self.assertEqual(key, key2)
 
+        # ensure comparison does not raise exception
+        assert key != None  # noqa: E711
+
     def test_11_load_ecdsa_password_256(self):
         key = ECDSAKey.from_private_key_file(_support('test_ecdsa_password_256.key'),
                                              b'television')
@@ -501,6 +510,9 @@ def test_ed25519(self):
         )
         self.assertNotEqual(key1.asbytes(), key2.asbytes())
 
+        # ensure comparison does not raise exception
+        assert key1 != None  # noqa: E711
+
     @pytest.mark.skipif("not Ed25519Key.is_supported()")
     def test_ed25519_compare(self):
         # verify that the private & public keys compare equal