Fixed tests introduced in previous commit on Python 2. Refs #20557.
Add `response_delete` and `render_delete_form` methods to `ModelAdmin`

This make it easier to control the delete flow.
Add docs for `response_add`, `response_change` and `response_delete`
RunSQL migration operation and alpha SeparateDatabaseAndState op'n.
Fixed 16992 -- Added InnoDB warning regarding reuse of AUTO_INCREMENT values.

Thanks kent at nsc.liu.se for the report.
Fixed an encoding issue in the test client.

Fixed
comment_tests.tests.test_comment_view.CommentViewTests.testCommentPostRedirectWithInvalidIntegerPK.

Refs #20530.
Oops :(
Improved docs for `contrib.admin.options.ModelAdmin.response_*`

Added links to code references in the docs for `response_add`,
`response_change` and `response_delete`.
Merge pull request #1592 from pablomouzo/fix-admin-view-response-methods-docs

Improved docs for `contrib.admin.options.ModelAdmin.response_*`