- Disable three more tests on git submodules:
* https://github.com/gitpython-developers/GitPython/issues/597
* test-skips.patch

- Update to version 3.1.0.1582544583.8c9da73:
* Replace invalid bytes when decoding TagObject stream
* Use UTF-8 encoding when getting information about a symbolic reference
* Remove and replace references to nose with unittest in documentation
* Remove nose from test requirements
* Replace nose with unittest in tox configuration
* Replace nose with unittest in Travis CI script
* Added changelog for unreleased changes
* Restrict gitdb2 version to <4
* Remove test.lib.asserts and use unittest.mock.patch directly
* Replace assert_false with assertFalse
* Replace assert_true with assertTrue
* Replace raises with assertRaises
* Replace assert_raises with assertRaises
* Replace assert_not_equal with assertNotEqual
* Replace assert_equal with assertEqual
* Remove and replace assert_match with assertRegex
* Remove old, no longer used assert methods
* Remove references to old mock library in documentation
* Remove outdated checks for unittest.mock existence
* Fix Python version requirement in documentation
* Remove badges for no longer existing Waffle site from README
* Add support for Python 3.8
* Replace deprecated Logger.warn with Logger.warning
* Replace deprecated assertRaisesRegexp alias with assertRaisesRegex
* Replace deprecated assertNotEquals alias with assertNotEqual