tests/test-issue1089.t

clippy: actually fail if there are any warnings

So far, only errors would trip the CI, this makes it so all warnings are
elevated to errors, making it a CI fail if any warnings are present.
This was the intended behavior, I just missed this when adding clippy.

https://bz.mercurial-scm.org/1089

  $ hg init repo
  $ cd repo
  $ mkdir a
  $ echo a > a/b
  $ hg ci -Am m
  adding a/b

  $ hg rm a
  removing a/b
  $ 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
  $ cd b

Relative delete:

  $ hg ci -m m ../a

  $ cd ..