BK since would stall if gzip or pigz is available, and not p7zip

…rue is probably not what you want

patool invokes with shell=True and behavior when cmd is provided as list
and shell is True is not what you would expect - only the first list member
is provided to the shell and the rest as additional arguments to the shell,
not as a part of the command. That leads to incorrect execution of the line

This test passes whenever p7zip-full is installed

Proper solution is a bit too involved, so postponed, and decided just to blow
with an informative message for now