Use new f-strings where possible

solvable/src/event_handler_main.py

@@ -12,7 +12,7 @@ LOG = logging.getLogger(__name__)
 
 def cenator(history):
     LOG.debug('User executed command: "%s"', history[-1])
-    MessageSender().send('JOHN CENA', 'You\'ve executed "{}"'.format(history[-1]))
+    MessageSender().send('JOHN CENA', f'You\'ve executed "{history[-1]}"')
 
 
 class TestCommands(TerminalCommands):

solvable/src/test_fsm.py

@@ -23,4 +23,4 @@ class TestFSM(LinearFSM):
         self.state_notify(5)
 
     def state_notify(self, state):
-        self.message_sender.send('TestFSM', 'Entered state {}!'.format(state))
+        self.message_sender.send('TestFSM', f'Entered state {state}!')