Stopped returning mirrors from setup_databases.

The return value of setup_databases is only used as an argument for
teardown_databases which doesn't need mirrors.

django/test/runner.py

@@ -183,8 +183,7 @@ class DiscoverRunner(object):
         """
         Destroys all the non-mirror databases.
         """
-        old_names, mirrors = old_config
-        for connection, old_name, destroy in old_names:
+        for connection, old_name, destroy in old_config:
             if destroy:
                 connection.creation.destroy_test_db(old_name, self.verbosity, self.keepdb)
 
@@ -374,7 +373,6 @@ def setup_databases(verbosity, interactive, keepdb=False, debug_sql=False, **kwa
     test_databases, mirrored_aliases = get_unique_databases_and_mirrors()
 
     old_names = []
-    mirrors = []
 
     for signature, (db_name, aliases) in test_databases.items():
         first_alias = None
@@ -396,7 +394,6 @@ def setup_databases(verbosity, interactive, keepdb=False, debug_sql=False, **kwa
                     connections[first_alias].settings_dict)
 
     for alias, mirror_alias in mirrored_aliases.items():
-        mirrors.append((alias, connections[alias].settings_dict['NAME']))
         connections[alias].creation.set_as_test_mirror(
             connections[mirror_alias].settings_dict)
 
@@ -404,4 +401,4 @@ def setup_databases(verbosity, interactive, keepdb=False, debug_sql=False, **kwa
         for alias in connections:
             connections[alias].force_debug_cursor = True
 
-    return old_names, mirrors
+    return old_names

docs/releases/1.9.txt

@@ -995,6 +995,7 @@ Miscellaneous
 * Private function ``django.utils.functional.total_ordering()`` has been
   removed. It contained a workaround for a ``functools.total_ordering()`` bug
   in Python versions older than 2.7.3.
+
 * XML serialization (either through :djadmin:`dumpdata` or the syndication
   framework) used to output any characters it received. Now if the content to
   be serialized contains any control characters not allowed in the XML 1.0
@@ -1023,6 +1024,12 @@ Miscellaneous
   as it's unused by the application. If your project or a third-party app makes
   use of it, :ref:`create a custom ModelAdmin <flatpages-admin>` to add it back.
 
+* The return value of
+  :meth:`~django.test.runner.DiscoverRunner.setup_databases` and the first
+  argument of :meth:`~django.test.runner.DiscoverRunner.teardown_databases`
+  changed. They used to be ``(old_names, mirrors)`` tuples. Now they're just
+  the first item, ``old_names``.
+
 .. _deprecated-features-1.9:
 
 Features deprecated in 1.9