Fixed #17883. Improved error message for old-style database backends.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17689 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/backends/dummy/base.py

@@ -12,7 +12,9 @@ from django.db.backends import *
 from django.db.backends.creation import BaseDatabaseCreation
 
 def complain(*args, **kwargs):
-    raise ImproperlyConfigured("You haven't set the database ENGINE setting yet.")
+    raise ImproperlyConfigured("settings.DATABASES is improperly configured. "
+                               "Please supply the ENGINE value. Check "
+                               "settings documentation for more details.")
 
 def ignore(*args, **kwargs):
     pass