Hello,
I'm starting a new discussion about compiling a file with Emacs. I will try
to be clear:

1. Compilation without Emacs in a terminal (Xterm):

 /home / aragorn / texlive / 2018 / bin / x86_64-linux / context Test.tex
Ok!

 / home / aragorn / context / tex / linux-64 / bin / context Test.tex Ok!

2. Compiling with a Emacs terminal shell command by having this in my ~ /
.emacs file

(setenv "PATH" "/ home / aragorn / context / tex / texmf-linux-64 / bin: $
PATH" t)

/ home / aragorn / texlive / 2018 / bin / x86_64-linux / context Test.tex
No Ok!

/ home / aragorn / context / tex / tex-linux-64 / bin / context Test.tex No
Ok!

3. Compiling with an Emacs terminal shell command by commenting this in my
~ / .emacs file

;; (setenv "PATH" "/ home / aragorn / context / tex / texmf-linux-64 / bin:
$ PATH" t)

/ home / aragorn / texlive / 2018 / bin / x86_64-linux / context Test.tex
Ok!

/ home / aragorn / context / tex / linux-64 / bin / context Test.tex Ok!

4. Compiling with the C-C C-C command by commenting this in my ~ / .emacs
file

;; (setenv "PATH" "/ home / aragorn / context / tex / texmf-linux-64 / bin:
$ PATH" t)

OK !

5. Coming with the C-c C-c command by having this in my ~ / .emacs file

(setenv "PATH" "/ home / aragorn / context / tex / texmf-linux-64 / bin: $
PATH" t) (that's what I do with all other files)

No OK !

Thanks.

My file Test.tex

% macros=mkvi
\setuppagenumbering[location=footer]

\startusableMPgraphic{NumberHead}
     draw outlinetext.f
         ("\bf\namedheadnumber{chapter}")
         (withcolor "lightgray")
         ysized 50pt ;
\stopusableMPgraphic

\unexpanded\def\processMPheadnumber#1%
  {\useMPgraphic{NumberHead}}

\setuphead
   [chapter]
   [command=\HeadTitle,
    headstyle=\ss,
    numbercommand=\processMPheadnumber,
   ]


\unexpanded\def\HeadTitle#1#2%
  {\framed
    [frame=off,
     bottomframe=on,
     width=broad,
     align={broad,nothyphenated,left}]
    {#1\blank[nowhite]#2}}

  \starttext
\starttitle[title={Sommaire}]

\start

    \placelist
      [chapter,section,subsection]
      [criterium=all,
       alternative=c]

\stop

\stoptitle



\startchapter[title=Espaces probabilisés]

\startsubsection[title=Expérience aléatoire et univers]

\stopsubsection

\startsubsection[title=Événements]

\stopsubsection

\stopchapter

\stoptext