Added warning silencers to some noisy tests.

These warnings all emerged as the result of the introduction of the checks framework.

Thanks to Anssi Kääriäinen for the report.

tests/admin_checks/tests.py

@@ -1,5 +1,7 @@
 from __future__ import unicode_literals
 
+import warnings
+
 from django import forms
 from django.contrib import admin
 from django.core import checks
@@ -425,12 +427,15 @@ class SystemChecksTestCase(TestCase):
         class MyModelAdmin(admin.ModelAdmin):
             validator_class = MyValidator
 
-        errors = MyModelAdmin.check(model=Song)
-        expected = [
-            checks.Error(
-                'error!',
-                hint=None,
-                obj=MyModelAdmin,
-            )
-        ]
-        self.assertEqual(errors, expected)
+        with warnings.catch_warnings(record=True):
+            warnings.filterwarnings('ignore', module='django.contrib.admin.options')
+            errors = MyModelAdmin.check(model=Song)
+
+            expected = [
+                checks.Error(
+                    'error!',
+                    hint=None,
+                    obj=MyModelAdmin,
+                )
+            ]
+            self.assertEqual(errors, expected)