[1.7.x] Fixed #23892 -- Clarified compatibility policy for migrations.

changes as it converts all the bytestring attributes to text strings; this is

normal and should only happen once.

Supporting multiple Django versions

-----------------------------------

If you are the maintainer of a third-party app with models, you may need to

ship migrations that support multiple Django versions. In this case, you should

always run :djadmin:`makemigrations` **with the lowest Django version you wish

to support**.

The migrations system will maintain backwards-compatibility according to the

same policy as the rest of Django, so migration files generated on Django X.Y

should run unchanged on Django X.Y+1. The migrations system does not promise

forwards-compatibility, however. New features may be added, and migration files

generated with newer versions of Django may not work on older versions.

.. _upgrading-from-south:

Upgrading from South