chrony_status: cleanup: use f-strings and fix/ignore pylint warnings

plugins/chrony/chrony_status

@@ -21,10 +21,10 @@ Unix domain socket which chronyc uses to communicate with chronyd. Example
 
 =head1 INTERPRETATION
 
-Monitor Chrony's stratum value (with warning), time offset, network delay, clock
-frequency, packets received, and packets dropped. It would be very easy to
-monitor all of Chrony's values, but IMHO they aren't needed. The most important
-information is stratum, giving "synced" / "not synced" value.
+Monitor Chrony's stratum value (with warning), time offset, network delay,
+clock frequency, packets received, and packets dropped. It would be very easy
+to monitor all of Chrony's values, but IMHO they aren't needed. The most
+important information is stratum, giving "synced" / "not synced" value.
 
 =head1 AUTHOR
 
@@ -94,9 +94,9 @@ def get_values():
         return {}
     lines = output.stdout.splitlines()
     ret = {}
-    for label in FIELDS:
+    for label, prefix in FIELDS.items():
         for line in lines:
-            if line.startswith(FIELDS[label]):
+            if line.startswith(prefix):
                 value = line.split(':', 1)[1].split()[0]
                 if ' slow' in line:
                     value = -float(value)
@@ -106,6 +106,7 @@ def get_values():
 
 def config():
     """Print plugin config."""
+    # pylint: disable=too-many-statements
     print('multigraph chrony_stratum')
     print('graph_title Chrony stratum')
     print('graph_vlabel stratum')
@@ -176,15 +177,15 @@ def fetch():
     """Print values."""
     values = get_values()
     for graph in GRAPHS:
-        print('multigraph chrony_{}'.format(graph))
+        print(f'multigraph chrony_{graph}')
         if graph == 'stratum' and values[graph] == '0':
-            print('{}.value U'.format(graph))
+            print(f'{graph}.value U')
         elif graph == 'serverstats':
             for stat in SERVERSTATS:
                 if stat in values:
-                    print('{}.value {}'.format(stat, values[stat]))
+                    print(f'{stat}.value {values[stat]}')
         else:
-            print('{}.value {}'.format(graph, values[graph]))
+            print(f'{graph}.value {values[graph]}')
 
 
 if __name__ == '__main__':