What does the following error message mean? `Undefined control sequence. <argument> \@Keywords l.4319 \ProcessKeyvalOptions{Hyp}`

Question

I got the following error message (Setup: Ububtu 14 LTS, TeXmaker, TeX Live 2013/Debian, pdfLaTeX):

log-file says:

! Undefined control sequence. <argument> \@Keywords l.4319 \ProcessKeyvalOptions{Hyp} 
The control sequence at the end of the top line of your error message was never \def'ed.

hyperref.sty says:

\ProcessKeyvalOptions{Hyp}
\def\Hy@xspace@end{}
\ltx@IfUndefined{xspaceaddexceptions}{%
  \Hy@AtBeginDocument{%
    \ltx@IfUndefined{xspaceaddexceptions}{%
    }{%
      \def\Hy@xspace@end{%
        \ltx@gobble{end for xspace}%
      }%
      \xspaceaddexceptions{%
        \Hy@xspace@end,\hyper@linkend,\hyper@anchorend
      }%
    }%
  }%
}

Any idea what it means?

MWE:

\RequirePackage[patch]{kvoptions} 
\documentclass{DissOnlineLatex}
%\usepackage[ngerman]{babel}
\usepackage[T1]{fontenc}
\usepackage{lscape}
\usepackage{setspace}
\usepackage[style=chem-angew,backend=bibtex8,]{biblatex}
\usepackage{hyperref}
\usepackage[printonlyused]{acronym}
\bibliography{Literatur.bib}
\onehalfspacing
\begin{document}
\end{document}

Answer 1

The error messages means, that \@Keywords is undefined.

\@Keywords is only defined by the class DissOnlineLatex, if \Keywords is used:

\newcommand*{\Keywords}[1]{\gdef\@Keywords{#1}}

\Keywords is invoked at the end of metadata.tex and should not be deleted. Set the appropriate keywords there.