config: clean up message about ignored untrusted config

The error message relied on Python's default formatting of arguments
to an Exception's constructor. Let's try to make it a little more
readable for users.

Differential Revision: https://phab.mercurial-scm.org/D9352

mercurial/ui.py

@@ -469,7 +469,9 b' class ui(object):'
             except error.ParseError as inst:
                 if trusted:
                     raise
-                self.warn(_(b'ignored: %s\n') % stringutil.forcebytestr(inst))
+                self.warn(
+                    _(b'ignored %s: %s\n') % (inst.location, inst.message)
+                )
 
         self._applyconfig(cfg, trusted, root)
 

tests/test-trusted.py.out

@@ -174,7 +174,7 b' quux'
 # parse error
 # different user, different group
 not trusting file .hg/hgrc from untrusted user abc, group def
-ignored: ('foo', '.hg/hgrc:1')
+ignored .hg/hgrc:1: foo
 # same user, same group
 hg: parse error at .hg/hgrc:1: foo