[Tex/LaTex] bug in tabu when rowcolors are defined

Question

In the following code the vertical separation from cell to the bottom is negative instead of the defined \tabulinesep=5pt when \rowcolor{headcolor} and and \rowfont are defined.

\documentclass[]{scrartcl} 
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage[utf8]{inputenc}
\usepackage[table]{xcolor}
\usepackage{tabu}
  \tabulinesep=5pt
\listfiles
\begin{document}
\colorlet{headcolor}{gray!25}
\begin{tabu} to 0.8\textwidth{X[1,L]X[1,L]}
    \hline
    \rowcolor{headcolor}
    \rowfont[l]{\bfseries}%
     head & head \tabularnewline
    \hline
    text which is considerably longer than the width of the column &
    text which is considerably longer than the width of the column \\
    \hline
\end{tabu}
\end{document}

Here the visual result

Is this a bug in the tabu package? I contacted the author of tabu, but got no answer in the last days.

Answer 1

\rowcolor is defined by colortbl. So it's an incompatibility between the two packages. You can fix that by using the tabu command \taburowcolors instead:

\colorlet{headcolor}{gray!25}
\begin{tabu} to 0.8\textwidth{X[1,L]X[1,L]}
    \hline
    \taburowcolors 1{headcolor .. headcolor}
    \rowfont[l]{\bfseries}%
     head & head \tabularnewline
    \taburowcolors 1{white .. white}
    \hline
    text which is considerably longer than the width of the column &
    text which is considerably longer than the width of the column \\
    \hline
\end{tabu}