tests/test-remotefilelog-wireproto.t

errors: raise ConfigError on failure to parse config file

This replaces two raises of `ParseError` by `ConfigError`, which makes
it so we get the desired exit code when `ui.detailed-exit-code` is
enabled. Because the exceptions include a location, I had to add that
to `ConfigError` as well. I considered making `ConfigError` a subclass
of `ParseError`, but it doesn't feel like it quite passes the "is-a"
test.

I used "config error: " as prefix for these errors instead of the
previous "hg: parse error: ", which seems a little less accurate now
(and, as I've said before, I don't know what the "hg: " part is
supposed to signify anyway). I can easily be convinced to change the
prefix to something else (including "abort: ").

Some of the exceptions raised here mean that we fail to even load the
`ui` object in the `dispatch` module. When that happens, we don't know
to use detailed exit codes, so some tests (e.g. `test-hgrc.t`) still
see exit code 255. I'll try to get back to that later. It should be
possible to give detailed exit codes if at least part of the config
can be read (e.g. when the system-wide one enables detailed exit codes
and the user's config fails to parse).

Differential Revision: https://phab.mercurial-scm.org/D9355

#require no-windows

  $ . "$TESTDIR/remotefilelog-library.sh"

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [remotefilelog]
  > server=True
  > EOF
  $ echo x > x
  $ hg commit -qAm x
  $ echo y >> x
  $ hg commit -qAm y
  $ echo z >> x
  $ hg commit -qAm z
  $ hg update 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo w >> x
  $ hg commit -qAm w

  $ cd ..

Shallow clone and activate getflogheads testing extension

  $ hgcloneshallow ssh://user@dummy/master shallow --noupdate
  streaming all changes
  2 files to transfer, 908 bytes of data
  transferred 908 bytes in * seconds (*/sec) (glob)
  searching for changes
  no changes found
  $ cd shallow

  $ cat >> .hg/hgrc <<EOF
  > [extensions]
  > getflogheads=$TESTDIR/remotefilelog-getflogheads.py
  > EOF

Get heads of a remotefilelog

  $ hg getflogheads x
  2797809ca5e9c2f307d82b1345e832f655fb99a2
  ca758b402ddc91e37e3113e1a97791b537e1b7bb

Get heads of a non-existing remotefilelog

  $ hg getflogheads y
  EMPTY