Unused imports

[py3k] tuple unpacking in function args

[py3k] ur'' is gone

[py3k] octals and long

[py3k] Fix raise with embedded traceback python 3 removed the raise syntax with 2 and 3 expressions.

[py3k] print function

[py3k] except as

[py3k] backtick to repr

[hooks/syncschema] make sure CWUniqueTogetherConstraintDelOp happens before CWConstraintDelOp SQLServer refuses to index an unlimited text column, so we should drop unique_together constraints (which imply an index) before we drop size constraints. Closes #5560601.

[hooks/syncschema] only call "ALTER TABLE" once when changing a size constraint Until now we would: - remove the old size constraint from the in-memory schema - call update_rdef_column which removes the size restriction from the column's type - add the new constraint object - call update_rdef_column which adds the size restriction back This breaks on SQL Server when the column is involved in an index (e.g. as part of a multi-column unique constraint), because in the intermediate stage the column's type is "nvarchar(max)", which is not indexable. Of course we must still detect the case where a size constraint is really dropped and update the db schema accordingly. Closes #5557633.