Fix a few little issues with 9.5 support (#3260)

1. pg_rewind error log format wasn't verbose
2. it doesn't support specifying num in synchronous_standby_names

tests/test_rewind.py

@@ -194,6 +194,14 @@ class TestRewind(BaseTestPostgresql):
             self.r.trigger_check_diverged_lsn()
             self.assertFalse(self.r.rewind_or_reinitialize_needed_and_possible(self.leader))
 
+            mock_popen.return_value.communicate.return_value = (
+                b'0, lsn: 0/040159C1, prev 0/\n',
+                b'pg_waldump: fatal: error in WAL record at 0/40159C1: invalid record length at 0/402DD98\n'
+            )
+            self.r.reset_state()
+            self.r.trigger_check_diverged_lsn()
+            self.assertFalse(self.r.rewind_or_reinitialize_needed_and_possible(self.leader))
+
             self.r.reset_state()
             self.r.trigger_check_diverged_lsn()
             mock_popen.side_effect = Exception

tests/test_sync.py

@@ -155,6 +155,17 @@ class TestSync(BaseTestPostgresql):
         mock_reload.assert_called()
         self.assertEqual(value_in_conf(), "synchronous_standby_names = '3 (a,b)'")
 
+        self.p._major_version = 90501
+        mock_reload.reset_mock()
+        self.s.set_synchronous_standby_names([], 1)
+        mock_reload.assert_called()
+        self.assertEqual(value_in_conf(), "synchronous_standby_names = '*'")
+
+        mock_reload.reset_mock()
+        self.s.set_synchronous_standby_names(['a-1'], 1)
+        mock_reload.assert_called()
+        self.assertEqual(value_in_conf(), "synchronous_standby_names = '\"a-1\"'")
+
     @patch.object(Postgresql, 'last_operation', Mock(return_value=1))
     def test_do_not_prick_yourself(self):
         self.p.name = self.leadermem.name