fix linting issues

smash/web/views/visit.py

@@ -119,8 +119,7 @@ def visit_mark(request, visit_id: int, as_what: str):
                        modification_author=worker,
                        previous_value=visit.is_finished,
                        new_value=True,
-                       modification_description='Worker "{}" marked visit from "{}" as finished'.format(worker,
-                                                                                                        visit.subject),
+                       modification_description=f'Worker "{worker}" marked visit from "{visit.subject}" as finished',
                        modified_field='is_finished',
                        request_path=request.path,
                        request_ip_addr=ip
@@ -143,14 +142,14 @@ def visit_add(request, subject_id=-1):
         return redirect('web.views.subject_visit_details', subject_id=subject_id)
 
     if not subject.can_schedule():
-        messages.error(request, "Visit cannot be added because the subject status is: {}".format(subject.status))
+        messages.error(request, f"Visit cannot be added because the subject status is: {subject.status}")
         return redirect('web.views.subject_visit_details', subject_id=subject_id)
 
     if request.method == 'POST':
         form = VisitAddForm(request.POST, request.FILES)
         args = {'form': form}
         if request.POST['subject'] != subject_id:
-            messages.add_message(request, messages.WARNING, 'The subject is invalid. Must be {}'.format(subject))
+            messages.add_message(request, messages.WARNING, f'The subject is invalid. Must be {subject}')
             return wrap_response(request, 'visits/add.html', args)
         if form.is_valid():
             visit = form.save()