[PATCH 04 of 10 py3] scmutil: convert exception to bytes in a Py3-friendly manner

[Yuya Nishihara]

On Mon, 29 May 2017 10:32:26 -0400, Augie Fackler wrote:
> # HG changeset patch
> # User Augie Fackler <raf at durin42.com>
> # Date 1496000686 14400
> #      Sun May 28 15:44:46 2017 -0400
> # Node ID 6e1ab7424617c7c7afca7faab559507c5e816a9c
> # Parent  f1ae981927af4d2d75e2a0bc58c733c9a90c085b
> scmutil: convert exception to bytes in a Py3-friendly manner
> 
> As far as I can tell, the Abort instance might contain localized data,
> so we need to str() then convert to bytes by hand.
> 
> diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
> --- a/mercurial/scmutil.py
> +++ b/mercurial/scmutil.py
> @@ -187,7 +187,10 @@ def callcatch(ui, func):
>              ui.warn(_("(%s)\n") % inst.hint)
>          return 1
>      except error.Abort as inst:
> -        ui.warn(_("abort: %s\n") % inst)
> +        msg = str(inst)
> +        if not isinstance(msg, bytes):
> +            msg = encoding.unitolocal(msg)
> +        ui.warn(_("abort: %s\n") % msg)

This works as follows on Python 3:

 1. str(inst) converts non-ascii bytes in b'\xXX' form
 2. escaped "b'...'" unicode is converted back to bytes

Perhaps we'll need to add __bytes__() to our exception classes.