failed make - "Missing number, treated as zero."

[theonesean]

Howdy,

My make process fails after generating the compiled_tex files.

Output of make:

pandoc main.tex -o software-testing-laboon-ebook.pdf \
		--pdf-engine xelatex \
		--top-level-division=chapter -N --toc --toc-depth=2 \
		-M documentclass="book" \
		-M classoption="twoside" \
		-M classoption="letterpaper" \
		-M geometry="margin=1.25in" \
		-M title="\Huge{\textbf{A Friendly Introduction\\\\to Software Testing}}" \
		-M author="\LARGE{Bill Laboon}" \
		-M date="{\Large\textcopyright~\textbf{2019-04-09}}\\\\Compiled in PDF\LaTeX{}\endgraf\textit{for AKS and CKN}"
Error producing PDF.
! Missing number, treated as zero.
<to be read again> 
                   \protect 
l.4641 ...ter}\rule{0.5\linewidth}{\linethickness}

make: *** [pdf] Error 43

grepping through the compiled_tex directory yields:

> grep -r linethickness .
./30_defects.tex:\begin{center}\rule{0.5\linewidth}{\linethickness}\end{center}
./30_defects.tex:\begin{center}\rule{0.5\linewidth}{\linethickness}\end{center}
./30_defects.tex:\begin{center}\rule{0.5\linewidth}{\linethickness}\end{center}
./85_interacting_with_stakeholders.tex:\begin{center}\rule{0.5\linewidth}{\linethickness}\end{center}

I'm on macOS Catalina, running zsh 5.7.1, GNU Make 3.81, pandoc 2.2.3.2 (compiled with pandoc-types 1.17.5.1, texmath 0.11.0.1, skylighting 0.7.2), and XeTeX 3.14159265-2.6-0.999991 (TeX Live 2019) (with kpathsea version 6.3.1).

Thanks!

[ejmg]

This is what I found when researching this error: Horizontal rule in latex output no longer works with recent texlive #5801

I haven't been able to craft a solution due to my lack of knowledge with how tex template files work. Trying to ack and sed the suggested solution into each generated fails to work, neither does adding it to main.tex.