[PATCH 4 of 5] lfs: handle URLErrors to add additional information

[Yuya Nishihara]

On Thu, 15 Nov 2018 21:53:53 -0500, Matt Harbison wrote:
> +  $ hg -R httpclone update default --config lfs.url=http://localhost:$HGPORT2/missing
> +  abort: LFS error: No connection could be made because the target machine actively refused it!

Globbed out this message. On my Linux box, it just says "Connection refused".