[PATCH STABLE v2] sslutil: guard against broken certifi installations (issue5406)

[Yuya Nishihara]

On Mon, 24 Oct 2016 05:19:14 -0500, Gábor Stefanik wrote:
> # HG changeset patch
> # User Gábor Stefanik <gabor.stefanik at nng.com>
> # Date 1476893174 -7200
> #      Wed Oct 19 18:06:14 2016 +0200
> # Branch stable
> # Node ID c3fe0e56546a44a7961354d4840cdcb82cbecefc
> # Parent  76c57e1fe79b0980b377b4f305635dea393d6315
> sslutil: guard against broken certifi installations (issue5406)
> 
> Certifi is currently incompatible with py2exe; the Python code for certifi gets
> included in library.zip, but not the cacert.pem file - and even if it were
> included, SSLContext can't load a cacert.pem file from library.zip.
> This currently makes it impossible to build a standalone Windows version of
> Mercurial.
> 
> Guard against this, and possibly other situations where a module with the name
> "certifi" exists, but is not usable.

Sounds good. Queued for stable, thanks.