hgview #234670 be robust against .hgguestrepo parse errors [validation pending]

i had a merge conflict in my .hgguestrepo file, so i wanted to start hgview in one of the included repositories to try and figure out the right resolution. hgview died with:

hg: parse error at /home/jcr/tmp/grshells/grshell-cubicweb-v2/.hgguestrepo:11: <<<<<<< local

prioritynormal
typebug
done in1.8.1
load left0.000
closed by#c1cc5c806c53 [nested] be robust against .hgguestrepo parse errors (closes #234670)