This patch is two-fold; first it ensure that Django does close everything in
request.FILES at the end of the request and secondly the storage system should
no longer close any files during save, it's up to the caller to handle that --
or let Django close the files at the end of the request.
Backport of e2efc8965e from master.
This (nearly) completes the work to isolate all the test modules from
each other. This is now more important as importing models from another
module will case PendingDeprecationWarnings if those modules are not in
INSTALLED_APPS. The only remaining obvious dependencies are:
- d.c.auth depends on d.c.admin (because of the is_admin flag to some
views), but this is not so important and d.c.admin is in
always_installed_apps
- test_client_regress depends on test_client. Eventually these should
become a single module, as the split serves no useful purpose.