tests/test-hgrc.out

run-tests: fix _checkhglib() so it's correct when using --with-hg.

Since this makes the warning less likely, upgrade it to a "real"
warning to stderr.

hg: config error at .../t/.hg/hgrc:1: 'invalid'
updating working directory
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
[paths]
default = .../foo%bar
default = .../foo%bar
bundle.mainreporoot=.../foobar
defaults.backout=-d "0 0"
defaults.commit=-d "0 0"
defaults.tag=-d "0 0"
paths.default=.../foo%bar
ui.slash=True