Fixed #25285 -- Provided unknown command message with plain django-admin.py

Thanks Maxime Lorant for the report and Tim Graham for suggesting
the improved comment.

django/core/management/__init__.py

@@ -177,8 +177,14 @@ class ManagementUtility(object):
         try:
             app_name = commands[subcommand]
         except KeyError:
-            # This might trigger ImproperlyConfigured (masked in get_commands)
-            settings.INSTALLED_APPS
+            if os.environ.get('DJANGO_SETTINGS_MODULE'):
+                # If `subcommand` is missing due to misconfigured settings, the
+                # following line will retrigger an ImproperlyConfigured exception
+                # (get_commands() swallows the original one) so the user is
+                # informed about it.
+                settings.INSTALLED_APPS
+            else:
+                sys.stderr.write("No Django settings specified.\n")
             sys.stderr.write("Unknown command: %r\nType '%s help' for usage.\n" %
                 (subcommand, self.prog_name))
             sys.exit(1)

tests/admin_scripts/tests.py

@@ -283,7 +283,8 @@ class DjangoAdminDefaultSettings(AdminScriptTestCase):
         args = ['noargs_command']
         out, err = self.run_django_admin(args)
         self.assertNoOutput(out)
-        self.assertOutput(err, "settings are not configured")
+        self.assertOutput(err, "No Django settings specified")
+        self.assertOutput(err, "Unknown command: 'noargs_command'")
 
     def test_custom_command_with_settings(self):
         "default: django-admin can execute user commands if settings are provided as argument"
@@ -351,7 +352,8 @@ class DjangoAdminFullPathDefaultSettings(AdminScriptTestCase):
         args = ['noargs_command']
         out, err = self.run_django_admin(args)
         self.assertNoOutput(out)
-        self.assertOutput(err, "settings are not configured")
+        self.assertOutput(err, "No Django settings specified")
+        self.assertOutput(err, "Unknown command: 'noargs_command'")
 
     def test_custom_command_with_settings(self):
         "fulldefault: django-admin can execute user commands if settings are provided as argument"
@@ -418,7 +420,8 @@ class DjangoAdminMinimalSettings(AdminScriptTestCase):
         args = ['noargs_command']
         out, err = self.run_django_admin(args)
         self.assertNoOutput(out)
-        self.assertOutput(err, "settings are not configured")
+        self.assertOutput(err, "No Django settings specified")
+        self.assertOutput(err, "Unknown command: 'noargs_command'")
 
     def test_custom_command_with_settings(self):
         "minimal: django-admin can't execute user commands, even if settings are provided as argument"
@@ -485,7 +488,8 @@ class DjangoAdminAlternateSettings(AdminScriptTestCase):
         args = ['noargs_command']
         out, err = self.run_django_admin(args)
         self.assertNoOutput(out)
-        self.assertOutput(err, "settings are not configured")
+        self.assertOutput(err, "No Django settings specified")
+        self.assertOutput(err, "Unknown command: 'noargs_command'")
 
     def test_custom_command_with_settings(self):
         "alternate: django-admin can execute user commands if settings are provided as argument"
@@ -555,7 +559,8 @@ class DjangoAdminMultipleSettings(AdminScriptTestCase):
         args = ['noargs_command']
         out, err = self.run_django_admin(args)
         self.assertNoOutput(out)
-        self.assertOutput(err, "settings are not configured")
+        self.assertOutput(err, "No Django settings specified")
+        self.assertOutput(err, "Unknown command: 'noargs_command'")
 
     def test_custom_command_with_settings(self):
         "alternate: django-admin can execute user commands if settings are provided as argument"
@@ -644,7 +649,8 @@ class DjangoAdminSettingsDirectory(AdminScriptTestCase):
         args = ['noargs_command']
         out, err = self.run_django_admin(args)
         self.assertNoOutput(out)
-        self.assertOutput(err, "settings are not configured")
+        self.assertOutput(err, "No Django settings specified")
+        self.assertOutput(err, "Unknown command: 'noargs_command'")
 
     def test_builtin_with_settings(self):
         "directory: django-admin builtin commands succeed if settings are provided as argument"