Fixed #15035 -- Fixed collectstatic management command to work with non-local storage backends correctly. Also refactored a bit code smell.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15154 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/regressiontests/staticfiles_tests/storage.py

@@ -0,0 +1,19 @@
+from datetime import datetime
+from django.core.files import storage
+
+class DummyStorage(storage.Storage):
+    """
+    A storage class that does implement modified_time() but raises
+    NotImplementedError when calling 
+    """
+    def _save(self, name, content):
+        return 'dummy'
+
+    def delete(self, name):
+        pass
+
+    def exists(self, name):
+        pass
+
+    def modified_time(self, name):
+        return datetime.date(1970, 1, 1)