bug#25001: 26.0.50; err=[-53] Error in the push function

[Eli Zaretskii <eliz@gnu.org>]

> From: Damien Cassou <damien@cassou.me>
> Date: Wed, 23 Nov 2016 16:45:35 +0100
> 
> I can't use jabber.el on Emacs master (works fine on Emacs 25.1). The
> problem seems to be this call from `gnutls-negotiate`:
> 
>     (gnutls-boot process 'gnutls-x509pki
>       '(:priority "NORMAL" :hostname "cassou.me" :loglevel 0
>       :min-prime-bits 256 :trustfiles
>       ("/etc/pki/tls/certs/ca-bundle.crt") :crlfiles nil :keylist nil
>       :verify-flags nil :verify-error t :callbacks nil))
> 
> More details below.
> 
> 
> In GNU Emacs 26.0.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.22.2)
>  of 2016-11-23 built on luz4
> Repository revision: d8a1a56f5bce64d6ea6ccecdf1aaa4eb3a9898da
> Windowing system distributor 'Fedora Project', version 11.0.11899902
> System Description:	Fedora release 25 (Twenty Five)
> 
> Recent messages:
> Result: -53 (#o377777777777777777713, #x3fffffffffffffcb)
> 
> Result: (:priority "NORMAL" :hostname "cassou.me" :loglevel 0 :min-prime-bits 256 :trustfiles ("/etc/pki/tls/certs/ca-bundle.crt") :crlfiles nil :keylist nil :verify-flags nil :verify-error (:hostname . t) :callbacks nil)
> 
> gnutls.el: (err=[-53] Error in the push function.) boot: (:priority NORMAL :hostname cassou.me :loglevel 0 :min-prime-bits 256 :trustfiles (/etc/pki/tls/certs/ca-bundle.crt) :crlfiles nil :keylist nil :verify-flags nil :verify-error (:hostname . t) :callbacks nil)

I don't understand this: Emacs defines push functions for GnuTLS only
on MS-Windows, whereas this is on GNU/Linux.  So how come GnuTLS
complains about some error in push function?