Fixed #29324 -- Made SECRET_KEY validation lazy (on first access).

django/conf/__init__.py

@@ -81,6 +81,8 @@ class LazySettings(LazyObject):
         # This is done here for performance reasons so the modified value is cached.
         if name in {'MEDIA_URL', 'STATIC_URL'} and val is not None:
             val = self._add_script_prefix(val)
+        elif name == 'SECRET_KEY' and not val:
+            raise ImproperlyConfigured("The SECRET_KEY setting must not be empty.")
 
         self.__dict__[name] = val
         return val
@@ -184,9 +186,6 @@ class Settings:
                 setattr(self, setting, setting_value)
                 self._explicit_settings.add(setting)
 
-        if not self.SECRET_KEY:
-            raise ImproperlyConfigured("The SECRET_KEY setting must not be empty.")
-
         if self.is_overridden('PASSWORD_RESET_TIMEOUT_DAYS'):
             if self.is_overridden('PASSWORD_RESET_TIMEOUT'):
                 raise ImproperlyConfigured(

django/contrib/auth/tokens.py

@@ -12,7 +12,10 @@ class PasswordResetTokenGenerator:
     """
     key_salt = "django.contrib.auth.tokens.PasswordResetTokenGenerator"
     algorithm = 'sha256'
-    secret = settings.SECRET_KEY
+    secret = None
+
+    def __init__(self):
+        self.secret = self.secret or settings.SECRET_KEY
 
     def make_token(self, user):
         """

django/core/checks/security/base.py

@@ -1,4 +1,5 @@
 from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
 
 from .. import Error, Tags, Warning, register
 
@@ -182,10 +183,14 @@ def check_ssl_redirect(app_configs, **kwargs):
 
 @register(Tags.security, deploy=True)
 def check_secret_key(app_configs, **kwargs):
+    try:
+        secret_key = settings.SECRET_KEY
+    except (ImproperlyConfigured, AttributeError):
+        passed_check = False
+    else:
         passed_check = (
-        getattr(settings, 'SECRET_KEY', None) and
-        len(set(settings.SECRET_KEY)) >= SECRET_KEY_MIN_UNIQUE_CHARACTERS and
-        len(settings.SECRET_KEY) >= SECRET_KEY_MIN_LENGTH
+            len(set(secret_key)) >= SECRET_KEY_MIN_UNIQUE_CHARACTERS and
+            len(secret_key) >= SECRET_KEY_MIN_LENGTH
         )
     return [] if passed_check else [W009]
 

docs/releases/3.2.txt

@@ -272,7 +272,13 @@ Requests and Responses
 Security
 ~~~~~~~~
 
-* ...
+* The :setting:`SECRET_KEY` setting is now checked for a valid value upon first
+  access, rather than when settings are first loaded. This enables running
+  management commands that do not rely on the ``SECRET_KEY`` without needing to
+  provide a value. As a consequence of this, calling
+  :func:`~django.conf.settings.configure` without providing a valid
+  ``SECRET_KEY``, and then going on to access ``settings.SECRET_KEY`` will now
+  raise an :exc:`~django.core.exceptions.ImproperlyConfigured` exception.
 
 Serialization
 ~~~~~~~~~~~~~

tests/settings_tests/tests.py

@@ -289,15 +289,11 @@ class SettingsTests(SimpleTestCase):
         with self.assertRaises(AttributeError):
             getattr(settings, 'TEST2')
 
+    @override_settings(SECRET_KEY='')
     def test_no_secret_key(self):
-        settings_module = ModuleType('fake_settings_module')
-        sys.modules['fake_settings_module'] = settings_module
         msg = 'The SECRET_KEY setting must not be empty.'
-        try:
         with self.assertRaisesMessage(ImproperlyConfigured, msg):
-                Settings('fake_settings_module')
-        finally:
-            del sys.modules['fake_settings_module']
+            settings.SECRET_KEY
 
     def test_no_settings_module(self):
         msg = (