Updated leftover format calls to f-strings.

main.py

@@ -24,14 +24,14 @@ class MoviesApp(App):
             budget = int(budget) * 1000000
             gross_revenue = int(gross_revenue) * 1000000
         except ValueError as exception:
-            self.root.ids.message.text = 'Formatting error: {exception}'.format(exception=exception)
+            self.root.ids.message.text = f'Formatting error: {exception}'
             return
         try:
             self._create_movie(self.session, title, budget, gross_revenue)
             self.root.ids.message.text = 'Movie added!'
         except SQLAlchemyError as exception:
             self.session.rollback()
-            self.root.ids.message.text = 'Database error: {exception}'.format(exception=exception)
+            self.root.ids.message.text = f'Database error: {exception}'
 
 
 def main():
@@ -40,7 +40,7 @@ def main():
         app.run()
     except SQLAlchemyError as exception:
         print('Initial database connection failed!', file=stderr)
-        print('Cause: {exception}'.format(exception=exception), file=stderr)
+        print(f'Cause: {exception}', file=stderr)
         exit(1)