Dear Maintainer,

Try compiling this simple file:

```
\documentclass{article}

\usepackage{fontspec}

\usepackage[autocompile]{gregoriotex}
\usepackage{shellesc}
\begin{document}

\write18{whereis gregorio}

\write18{gregorio --version}

% the gabc code
% size of the initial line
\gresetinitiallines{0}
\grechangestyle{initial}{16.56pt}
% use red lines
\gresetlinecolor{gregoriocolor}
\grechangestaffsize{13}
\gresetgregoriofont{greciliae}
\gabcsnippet{(c3 h!jij h)}
\end{document}
```

It will fail with a misleading error (shell escape not enabled).

It works with the current release 6.1.0.