pdflatex with simple Feynman

[Haines Brown]

I have no trouble witn Feynman diagrams in a LuaLaTeX document, but 
find it difficult to construct one in a LaTeX document. I construct a 
c.tex file with the sample from the fmf manual:

  \documentclass[12pt]{article}
  \usepackage[utf8]{inputenc}
  \usepackage[T1]{fontenc}
  \usepackage{feynmp-auto}
  \begin{document}
    \begin{fmffile}
    \begin{fmfgraph*}(40,30) 
      \fmfpen{thick}
      \fmfleft{i1,i2} 
      \fmfright{o1,o2}
      \fmf{fermion}{i1,v1,o1} 
      \fmf{fermion}{i2,v2,o2}
      \fmf{photon,label=$q$}{v1,v2} 
      \fmfdot{v1,v2}
    \end{fmfgraph*}
    \end{fmfile}
  \end{document}

When I do $ pdflatex c.tex I get error:

  ...
  [Loading MPS to PDF converter (version 2006.09.02).] ) 
  (/usr/local/texlive/2022/texmf-dist/tex/latex/epstopdf-pkg/epstopdf-base.sty
  (/usr/local/texlive/2022/texmf-dist/tex/latex/latexconfig/epstopdf-sys.cfg))
  ! Argument of \begin  has an extra }.  

If from a command prompt before running pdflatex I do:

  $ fm \mode=localfile;' input c.tex

in the result c.log I get 

  ! Forbidden token found while scanning to the end of the statement.
  <inserted text>
                ;
  <to be read again>
                   end
  l.11 \end
         {fmfgraph*}
  A previous error seems to have propagated,
  causing me to read past where you wanted me to stop.
  I'll try to recover; but if the error is serious,
  you'd better type `E' or `X' now and fix your file.


-- 

     Haines Brown 
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