[PATCH 2 of 2 STABLE V3] py3: fix patchbomb to accept non-ASCII header value for email preview

[Augie Fackler]

On Wed, Oct 30, 2019 at 10:02:23PM +0900, Yuya Nishihara wrote:
> # HG changeset patch
> # User Yuya Nishihara <yuya at tcha.org>
> # Date 1572439788 -32400
> #      Wed Oct 30 21:49:48 2019 +0900
> # Branch stable
> # Node ID 3b53b4da70668d5abd27993778fe2da0606aca45
> # Parent  e7add06518eeebeb236a97ab051bb55e95c591b8
> py3: fix patchbomb to accept non-ASCII header value for email preview

queued for stable, thanks