templater: don't blow up when trying to build an abort message
__name__ is unicode, but we need bytes. For now, we'll make the
(mostly-safe) assumption that template filter names will be ascii.
Differential Revision: https://phab.mercurial-scm.org/D1137
https://bz.mercurial-scm.org/1089
$ hg init
$ mkdir a
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b (glob)
$ hg ci -m m a
$ mkdir a b
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b (glob)
$ cd b
Relative delete:
$ hg ci -m m ../a
$ cd ..