Thanks to charettes and priidukull for investigating the issue, and to
kurevin for the report.
Backport of 355c5edd9390caad5725375abca03460805f663b from master
Fixed queries where an expression was used in order_by() but the
expression wasn't in the query's select clause (for example the
expression could be masked by .values() call)
Thanks to Trac alias MattBlack85 for the report.
Backport of fb5c7748da from master.
This also prevents state modifications from corrupting previous states.
Previously, when a model defining a relation was unregistered first,
clearing the cache would cause its related models' _meta to be cleared
and would result in the old models losing track of their relations.
Backport of 0385dad073270c37f8c4a5f13edce43f2a69ba8a from master
Fixed MigrationWriter.serialize() to correctly handle migration
operations by utilizing OperationWriter.
Thanks Piotr Maliński for the report.
Backport of e8e4f978dd4b7a3d0c689c6e3301e3c6f9e50003 from master
get_language() can return None when translations are deactivated.
Thanks Nicola Peduzzi for the reporti and Tim Graham for the review.
Backport of 7a0d9b5cda from master.
