BibLaTeX changing the character at error/warning message

[pauloney]

When I refer to a record with a wrong key (in the example below: Frégier instead of Frégier-1816) biblatex changes the accented character é to é, at the error message level.

\documentclass{report}

\begin{filecontents}{\jobname.bib}
@article{Frégier-1816,
    author = {Frégier, Paul Félix},
    title = {Géométrie analitique. Théorèmes nouveuax sur les lignes},
    journal = {Annales de mathématiques pures et appliquées},
    volume = {7},
    year = {1816--1817},
    pages = {95--98},
    hyphenation = {french},
}
\end{filecontents}

\usepackage{biblatex}
\addbibresource{\jobname.bib}

\begin{document}
Lorem ipsum~\cite{Frégier} dolor sit amet.
\printbibliography
\end{document}

The LaTeX error message uses the correct é:

LaTeX Warning: Citation 'Frégier' on page 1 undefined on input line 19.

But the Biber run, changes it to another different character é:

WARN - I didn't find a database entry for 'Frégier' (section 0)

It is not visible here because of the font used in this web-page, but of you copy both
to your editor, you can see the difference:

This is extremely annoying because the differences in some of these characters are hard to spot and you can no longer Copy & Paste to locate the problematic key on your files.

[plk]

Apologies for taking so long to look at this - it was indeed a bug - you can try biber 2.20 DEV from SF with biblatex 3.20 to test. biber should now use NFC form for such errors, like latex does.

[plk]

2.20 is now released