test_string.diff looks good, except that it should probably only test the exception type, not the message (they are not a guaranteed part of the Python language and may change arbitrarily between versions or implementations (e.g. PyPy), so better not to add tests that depend on exact words).

I don’t have anything specific to say about issue13598.diff; if it makes the test pass, then it’s good.  “if manual == True” should just be replaced by “if manual”.

If you’d like to, you can make one patch with fix + tests that addresses my comments and remove the older diffs.