rmail-convert-mime-header and missing metamail

[Daniel R. Grayson]

Due to a system upgrade here, the program metamail was removed.  I had
the line

        (setq rmail-message-filter 'rmail-convert-mime-header)

in my .emacs.  The symptom was that many email messages lost all of their
headers.  There should be a more graceful way for that function to fail when
metamail fails to execute.

Meanwhile, commenting out that line helps preserve the headers of my email.

Signaling: (file-error "Searching for program" "no such file or directory" 
"metamail")
  call-process("metamail" nil t nil "-x" "-d" "-z" "-c" "text/plain" "-E" 
"7bit" "-m" "emacs" "/tmp/metamail25111ffF")
  apply(call-process "metamail" nil t nil ("-x" "-d" "-z" "-c" "text/plain" 
"-E" "7bit" "-m" "emacs" "/tmp/metamail25111ffF"))
  metamail-region(778443 779414 nil nil nodisplay)
  metamail-interpret-header()
  (if (save-restriction (narrow-to-region ... ...) (mail-fetch-field 
"Mime-Version")) (metamail-interpret-header))
  (save-excursion (if (save-restriction ... ...) (metamail-interpret-header)))
  rmail-convert-mime-header()
  rmail-reformat-message(777453 779336)
  rmail-show-message(64)
  rmail-next-undeleted-message(1)
* call-interactively(rmail-next-undeleted-message)

(emacs-version)
"GNU Emacs 20.7.1 (sparc-sun-solaris2.7, X toolkit)
 of Sun Aug 20 2000 on jupiter.math.uiuc.edu"