Refs #29469 -- Reused get_app_config() error message in makemigrations error.

django/core/management/commands/makemigrations.py

@@ -65,23 +65,14 @@ class Command(BaseCommand):
 
         # Make sure the app they asked for exists
         app_labels = set(app_labels)
-        bad_app_labels = set()
+        has_bad_labels = False
         for app_label in app_labels:
             try:
                 apps.get_app_config(app_label)
-            except LookupError:
-                bad_app_labels.add(app_label)
-        if bad_app_labels:
-            for app_label in bad_app_labels:
-                if '.' in app_label:
-                    self.stderr.write(
-                        "'%s' is not a valid app label. Did you mean '%s'?" % (
-                            app_label,
-                            app_label.split('.')[-1],
-                        )
-                    )
-                else:
-                    self.stderr.write("App '%s' could not be found. Is it in INSTALLED_APPS?" % app_label)
+            except LookupError as err:
+                self.stderr.write(str(err))
+                has_bad_labels = True
+        if has_bad_labels:
             sys.exit(2)
 
         # Load the current graph state. Pass in None for the connection so

tests/migrations/test_commands.py

@@ -1408,20 +1408,20 @@ class AppLabelErrorTests(TestCase):
     app. 'django.contrib.auth' must be in INSTALLED_APPS for some of these
     tests.
     """
+    nonexistent_app_error = "No installed app with label 'nonexistent_app'."
+    did_you_mean_auth_error = (
+        "No installed app with label 'django.contrib.auth'. Did you mean "
+        "'auth'?"
+    )
+
     def test_makemigrations_nonexistent_app_label(self):
         err = io.StringIO()
         with self.assertRaises(SystemExit):
             call_command('makemigrations', 'nonexistent_app', stderr=err)
-        self.assertIn(
-            "App 'nonexistent_app' could not be found. Is it in "
-            "INSTALLED_APPS?", err.getvalue()
-        )
+        self.assertIn(self.nonexistent_app_error, err.getvalue())
 
     def test_makemigrations_app_name_specified_as_label(self):
         err = io.StringIO()
         with self.assertRaises(SystemExit):
             call_command('makemigrations', 'django.contrib.auth', stderr=err)
-        self.assertIn(
-            "'django.contrib.auth' is not a valid app label. Did you mean 'auth'?",
-            err.getvalue()
-        )
+        self.assertIn(self.did_you_mean_auth_error, err.getvalue())