Tabu very recently stopped working with color/xcolor or with fancyvrb

Question

Below is a MWE with a tabu table that compiled perfectly fine up until I updated packages today (Dec. 16, 2018) with TeX Live Utility.

\documentclass[11pt]{article}

\usepackage{amsmath}
\usepackage{xcolor}
\usepackage{tabu}

\title{Example}
\author{Andrew Turner}

\begin{document}
\maketitle

\begin{table}[h!]
    \centering

    \tabulinesep = 3pt

    \begin{tabu} spread 0pt {X[c$$]X[c$$]} \hline
        a & b \\ \hline
    \end{tabu}

    \caption{test}
\end{table}

\end{document}

After the update, trying to compile gives a whole bunch of errors like this:

! Missing \cr inserted.
<inserted text> 
                \cr 
l.19 \end{tabu}

I'm guessing that you meant to end an alignment here.

! Misplaced \cr.
<inserted text> \cr 

l.19 \end{tabu}

I can't figure out why you would want to use a tab mark
or \cr or \span just now. If something like a right brace
up above has ended a previous alignment prematurely,
you're probably due for more error messages, and you
might try typing `S' now just to see what is salvageable.

If I comment out the xcolor package, this fixes the issue, or if I get rid of the spread 0pt and keep the xcolor package this also fixes the issue. I looked at what just updated in TeX Live Utility, and I wonder if it has to do with the recent update of colortbl.

Any help would be greatly appreciated.

---

Here is a further example. This is actually exact same, as recent version(s) of fancyvrb require package xcolor.

this is obsolete since release 3.2 (2019/01/08) of fancyvrb which does not load xcolor anymore.

\documentclass{article}
\usepackage{fancyvrb}
\usepackage{tabu}
\begin{document}
\begin{tabu}spread 0pt {XX}
A
&
B
\end{tabu}
\end{document}

breaks with

! Missing } inserted.
<inserted text> 
                }
l.10 \end{tabu}

? 

Simply commenting out loading of fancyvrb it compiles, or using TL2017 (my TL2018 is already fully updated...) it compiles also.

Answer 1

UPDATE 2019-01-14

An equivalent patch has been applied in tabu 2.9 which has been submitted to ctan.

---

This is due to fixing a color leak in p-columns in array which is used underneath tabu, longtable tabularx etc. The tabu package overwrites a number of array internals assuming an internal structure (and grouping levels) which doesn't any any longer exist the moment a color package is loaded.

After staring at the tabu code for a while I think (but I'm not yet sure) that it only needs adding \color@begingroup in one place.

\usepackage{etoolbox}
\makeatletter
\patchcmd\tabu@startpboxmeasure
  {\aftergroup\tabu@endpboxmeasure}
  {\aftergroup\tabu@endpboxmeasure
   \color@begingroup
  }{\typeout{tabu patched}}{\typeout{tabu patch failed!}}
\patchcmd\tabu@LT@startpbox
  {\bgroup}{\bgroup\color@begingroup}
  {\typeout{tabu patched}}{\typeout{tabu patch failed!}} 
\makeatletter

This does fix the sample document above and the tests that I made so far. If others could check with their documents I would appreciate that. Of course in the end that or something else would then need to go into the tabu code.

Update

Added a second patch in above needed to account for the same change made to longtable. Thanks to Ulrike Fischer for providing it (in a different question).