tell user to choose different username

pretix_keycloak_create_user/signals.py

@@ -148,6 +148,6 @@ def validate_order(sender, positions, **kwargs):
         if response.status_code == 200:
             if json.loads(response.text) > 0:
                 raise OrderError(
-                    _("Username already taken. Please choose another username.")
+                    _("Username already taken")
                 )