Undefined control sequence

[marcthenarc]

I generated my .tex file without error.
Then I ran the following, just like indicated.

xelatex mydeck.tex

This is what I get:

This is XeTeX, Version 3.14159265-2.6-0.99998 (TeX Live 2017/Debian) (preloaded format=xelatex)
 restricted \write18 enabled.
entering extended mode
(./mydeck.tex
LaTeX2e <2017-04-15>
Babel <3.18> and hyphenation patterns for 3 language(s) loaded.
(/usr/share/texlive/texmf-dist/tex/latex/flashcards/flashcards.cls
Document Class: flashcards 2010/08/13 1.0.1 ([email protected])
(/usr/share/texlive/texmf-dist/tex/latex/base/ifthen.sty)
(/usr/share/texlive/texmf-dist/tex/latex/base/article.cls
Document Class: article 2014/09/29 v1.4h Standard LaTeX document class
(/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo))
Coudln't find papera4_portrait.cfg, using defualt.
! Undefined control sequence.
\reserved@b ...@onefilewithoptions #1[{\cardpaper
                                                  }][{}]\noexpand \@pkgexten...
l.77 \setlength
               {\oddevenshift}{\oddoffset}

Do this have to do with A4 support ?