fix typo

newsletter/models.py

@@ -63,7 +63,7 @@ class Subscriber(models.Model):
 
     def subscribe_in_mailman(self):
         try:
-            subprocess.run(['listadmin', '--add-member', self.email, settings.NEWSLETTER_NAME], checkTrue)
+            subprocess.run(['listadmin', '--add-member', self.email, settings.NEWSLETTER_NAME], check=True)
         except subprocess.CalledProcessError:
             # maybe an error because email is already registered?
             result = subprocess.run(