Don't try calling a non existing leader in patronictl pause (#1542)

While pausing a cluster without a leader on K8s patronictl was showing warnings that member "None" could not be accessed.

patroni/ctl.py

@@ -942,7 +942,7 @@ def toggle_pause(config, cluster_name, paused, wait):
         raise PatroniCtlException('Cluster is {0} paused'.format(paused and 'already' or 'not'))
 
     members = []
-    if cluster.leader:
+    if cluster.leader and cluster.leader.member.api_url:
         members.append(cluster.leader.member)
     members.extend([m for m in cluster.members if m.api_url and (not members or members[0].name != m.name)])
 
@@ -1008,7 +1008,7 @@ def show_diff(before_editing, after_editing):
     If the output is to a tty the diff will be colored. Inputs are expected to be unicode strings.
     """
     def listify(string):
-        return [l+'\n' for l in string.rstrip('\n').split('\n')]
+        return [line + '\n' for line in string.rstrip('\n').split('\n')]
 
     unified_diff = difflib.unified_diff(listify(before_editing), listify(after_editing))
 

patroni/ha.py

@@ -523,7 +523,7 @@ class Ha(object):
             if cluster_history:
                 self.dcs.set_history_value('[]')
         elif not cluster_history or cluster_history[-1][0] != master_timeline - 1 or len(cluster_history[-1]) != 4:
-            cluster_history = {l[0]: l for l in cluster_history or []}
+            cluster_history = {line[0]: line for line in cluster_history or []}
             history = self.state_handler.get_history(master_timeline)
             if history:
                 history = history[-self.cluster.config.max_timelines_history:]

patroni/postgresql/__init__.py

@@ -655,7 +655,6 @@ class Postgresql(object):
 
     def controldata(self):
         """ return the contents of pg_controldata, or non-True value if pg_controldata call failed """
-        result = {}
         # Don't try to call pg_controldata during backup restore
         if self._version_file_exists() and self.state != 'creating replica':
             try:
@@ -663,13 +662,12 @@ class Postgresql(object):
                 env.update(LANG='C', LC_ALL='C')
                 data = subprocess.check_output([self.pgcommand('pg_controldata'), self._data_dir], env=env)
                 if data:
-                    data = data.decode('utf-8').splitlines()
+                    data = filter(lambda e: ':' in e, data.decode('utf-8').splitlines())
                     # pg_controldata output depends on major version. Some of parameters are prefixed by 'Current '
-                    result = {l.split(':')[0].replace('Current ', '', 1): l.split(':', 1)[1].strip() for l in data
-                              if l and ':' in l}
+                    return {k.replace('Current ', '', 1): v.strip() for k, v in map(lambda e: e.split(':', 1), data)}
             except subprocess.CalledProcessError:
                 logger.exception("Error when calling pg_controldata")
-        return result
+        return {}
 
     @contextmanager
     def get_replication_connection_cursor(self, host='localhost', port=5432, **kwargs):