The kiwi.pdf file as provided in the kiwi-man-pages package
was never really used by our users but comes with a huge
dependency chain to LaTex. We provide the documentation
online as well as converted to DocBook from where all other
formats could be derived. Thus there is no need for us to
produce an extra PDF document which is imho never consulted.
In addition to this change also the contributing chapter has
been reworked. Due to recent changes and drop of obsolete
components from kiwi as well as the effort to move the development
setup to poetry, there is only one non python tool needed
for the development of kiwi. The check for this tool has been
moved into the Makefile and all other checks formerly done
in the helper/install_devel_packages script were deleted.
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