Log Message:
py-ruamel-yaml: update to 0.17.28.

[0, 17, 28]: 2023-05-26
  - fix for issue 464: documents ending with document end marker without final \ 
newline
    fail to load (reported by `Mariusz Rusiniak \ 
<https://sourceforge.net/u/r2dan/profile/>`__)

[0, 17, 27]: 2023-05-25
  - fix issue with inline mappings as value for merge keys
    (reported by Sirish on `StackOverflow \ 
<https://stackoverflow.com/q/76331049/1307905>`__)
  - fix for 468, error inserting after accessing merge attribute on ``CommentedMap``
    (reported by `Bastien gerard <https://sourceforge.net/u/bagerard/>`__)
  - fix for issue 461 pop + insert on same `CommentedMap` key throwing error
    (reported by `John Thorvald Wodder II \ 
<https://sourceforge.net/u/jwodder/profile/>`__)