/usr/share/emacs/site-lisp/tex-site.el

  (defvar TeX-lisp-directory "/var/usr/share/emacs/site-lisp/auctex/"
  "*The directory where the AUC TeX lisp files are located.")

  should be changed to

  (defvar TeX-lisp-directory "/usr/share/emacs/site-lisp/auctex/"
  "*The directory where the AUC TeX lisp files are located.")

  Personally, I would prefer a complete tex-site.el, e.g., with
  correct 

  (defcustom TeX-macro-global '("/usr/share/texmf/tex/")
  "Directories containing the sites TeX macro files and style files.
  The directory names *must* end with a slash   ."
  :group 'TeX-file  
  :type '(repeat (directory :format "%v")))


  If needed I can provide my tex-site.el.