using tabularx 2.09 in a \newenvironment produces errors

Question

The tabularx package with new version 2014/04/22 v2.09 produces errors with the following code which compiled without errors before:

\documentclass{article}

\usepackage{array}
\usepackage{tabularx}

\def\myfooA{\tabularx{\linewidth}{|X|}}
\def\myfooB{\endtabularx}

\newenvironment{myfoo}{\myfooA}{\myfooB}

\begin{document}

\begin{myfoo}
Test
\end{myfoo}

\end{document}

I do need \myfooA and \myfooB for my application, so I can't use \tabularx inside the environment definition directly (which would work with the new tabularx version).

How do I have to change \myfooA and \myfooB to work with \tabularx 2.09 ?

Addendum: Here is a MWE for the application which stopped to work:

\documentclass{article}
\usepackage{array}
\usepackage{tabularx}

\usepackage[table]{xcolor}
\usepackage{tcolorbox}

\begin{document}

\begin{tcolorbox}[tabularx={X},title=My table]
Group
\end{tcolorbox}

\end{document}

Update: The problem was solved by David Carlisle with tabularx v2.10

Answer 1

As LariFari indicated it required an optimistic reading of the documentation to suggest that it should have worked before, or that it works now, but it did work before, so I'm inclined to think it's a bug that it doesn't work in tabularx 2.09.

latex/required/tools has been updated on ctan with tabularx 2.10 which once again allows this usage.

I'm deleting the workaround initially posted here as it was only needed for a few days, and was not that robust.