tests: use readlink.py instead of readlink
The latter doesn't always exist, such as on Solaris-derived platforms.
Differential Revision: https://phab.mercurial-scm.org/D999
%include map-cmdline.default
changeset = '{cset}{branches}{bookmarks}{tags}{lphase}{parents}{user}{ldate}{summary}\n'
changeset_verbose = '{cset}{branches}{bookmarks}{tags}{lphase}{parents}{user}{ldate}{lfiles}{lfile_copies_switch}{description}\n'