logilab-devtools #35763 breaks if .hg/hgrc is missing [deprecated]

if .hg/hgrc is missing lgp check raises a mercurial.error.RepoError and prints a traceback before exiting.

a nicer error message and an explanation are needed.

prioritynormal
typebug
done in0.18.0
load0.000
load left0.000
closed by<not specified>