tests: print the server error log in `test-url-download.t`
There was a stray 500 error in CI, but no additional context to know what the
issue was.
https://foss.heptapod.net/octobus/mercurial-devel/-/jobs/163093
Differential Revision: https://phab.mercurial-scm.org/D9949
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
end_of_line = lf
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true
end_of_line = lf
[*.t]
indent_size = 2
indent_style = space
trim_trailing_whitespace = false
end_of_line = lf