Took advantage of django.utils.six.moves.urllib.*.
Fixed #21047 -- Added CLA mesage on the new contributor advice doc
Fixed #21035 -- Changed docs to treat the acronym SQL phonetically.

The documentation and comments now all use 'an' to
refer to the word SQL and not 'a'.
Fixed #21014 -- Fixed gobbled ImportError in MigrationLoader.
Fixed #21015 -- Fixed MigrationLoader when importlib.import_module returns a file module or an empty directory.
Fixed #16096 -- Added origin attribute to template instances.

Thanks jdunck for the suggestion.
Fixed #20977 -- Fixed writing migrations to disk on Python 3
ignore build directory, so it doesn't accidentally get committed
Fixed #18719 -- Made force_bytes more consistent with force_text.
Fixed #21052 -- Small performance optimization.
Make db.migrations ignore South-style migrations.
Merge pull request #1557 from garrypolley/remove-build-address

Added /build/ to .gitignore, so it doesn't accidentally get committed
Add --list option to migrate command
Fix SchemaEditor.__exit__ to handle exceptions correctly
Fixed #10164 -- Made AutoField increase monotonically on SQLite

Thanks malte for the report.
documented RelatedManager calling save() behind the scenes, added section on direct replacement of related object set
Fixed #20975 -- Fixed identation in docs/internals/committers.txt

Thanks EvilDMP for the report.
Merge pull request #1560 from technivore/ticket_20970

Related Fields documentation improvements
Fixed #21029: Test for previously-commited SchemaEditor.__exit__ bug.
Project/ModelState now correctly serialize multi-model inheritance