testing/py3-shtab: upgrade to 1.6.1
https://github.com/iterative/shtab/releases/tag/v1.6.0
https://github.com/iterative/shtab/releases/tag/v1.6.1
( all releases are marked as beta for some reason )
https://github.com/iterative/shtab/releases/tag/v1.6.0
https://github.com/iterative/shtab/releases/tag/v1.6.1
( all releases are marked as beta for some reason )