Revert "Fixed #12288 -- Validated that app names in INSTALLED_APPS ar…

…e unique"

This reverts commit c1ec089.

There are backwards compatability concerns with this.

django/conf/__init__.py

@@ -109,9 +109,8 @@ def __setattr__(self, name, value):
                 "to a tuple, not a string.")
         elif name == "INSTALLED_APPS":
             value = list(value)  # force evaluation of generators on Python 3
-            apps = [s.split('.')[-1] for s in value]
-            if len(value) != len(set(apps)):
-                raise ImproperlyConfigured("The INSTALLED_APPS setting must contain unique app names.")
+            if len(value) != len(set(value)):
+                raise ImproperlyConfigured("The INSTALLED_APPS setting must contain unique values.")
 
         object.__setattr__(self, name, value)
 

tests/settings_tests/tests.py

@@ -241,14 +241,11 @@ def tearDown(self):
     def test_unique(self):
         """
         An ImproperlyConfigured exception is raised if the INSTALLED_APPS contains
-        any duplicate appication names.
+        any duplicate strings.
         """
         with self.assertRaises(ImproperlyConfigured):
             self.settings_module.INSTALLED_APPS = ("myApp1", "myApp1", "myApp2", "myApp3")
 
-        with self.assertRaises(ImproperlyConfigured):
-            self.settings_module.INSTALLED_APPS = ("package1.myApp1", "package2.myApp1")
-
 
 class TrailingSlashURLTests(TestCase):
     """