Undefined control sequence \current at color with texlive 2020

[Enrico Gregorio]

> On 4 Jan 2021, at 20:24 , Detlev Droege <droege at uni-koblenz.de> wrote:
> 
> Hi experts,
> 
> one of our internal document classes suddenly throws an
> "Undefined control sequence" error after upgrading to TeXlive 2020.
> 
> I could boil it down to this minimal input:
> -----------------
> \documentclass{dinbrief}
> \usepackage{xcolor}
> 
> \begin{document}
>  Some text.
> \end{document}
> ————————

The class redefines \document and \enddocument,
which has always been a very bad thing to do since
the first release of LaTeX2e.

Apparently, they do it just for injecting a compatibility
layer for LaTeX2.09.

Ciao
Enrico