build: install python-dbusmock via pip for a Docker container (#18589)
build: install python-dbusmock via pip for a Docker container (#18589)

* build: use python-dbusmock v0.18.1 on Linux

To prevent timeout errors with some other python-dbusmock versions.

* Don't use a fixed version of python-dbusmock

Co-Authored-By: John Kleinschmidt <58e920f43df1b19b57b661762f7747563e5f3062@github.com>

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