bug#19326: 24.4; tex-validate-buffer error "Buffer is read-only"

[Kevin Ryde <user42_kevin@yahoo.com.au>]

Running

    emacs -Q /tmp/foo.tex
    M-x tex-validate-buffer
    =>
    error: Buffer is read-only: #<buffer *Occur*>

I hoped it would say something, or nothing, about the buffer -- an empty
buffer in this case.

It looks like occur-mode may set the occur buffer read-only which
tex-validate-buffer doesn't expect when writing its output there.


In GNU Emacs 24.4.1 (i586-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2014-10-26 on x86-csail-01, modified by Debian
Configured using:
 `configure --build i586-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 --enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.4/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.4/site-lisp:/usr/share/emacs/site-lisp
 --build i586-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
 --libexecdir=/usr/lib --localstatedir=/var/lib
 --infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes
 --enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.4/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.4/site-lisp:/usr/share/emacs/site-lisp
 --with-x=yes --with-x-toolkit=lucid --with-toolkit-scroll-bars
 --without-gconf --without-gsettings 'CFLAGS=-g -O2
 -fstack-protector-strong -Wformat -Werror=format-security -Wall'
 CPPFLAGS=-D_FORTIFY_SOURCE=2 LDFLAGS=-Wl,-z,relro'

Important settings:
  value of $LANG: en_AU.utf8
  locale-coding-system: utf-8-unix