use xetex to generate pdf

To correctly handle unicode art in code blocks...

docs/Makefile

@@ -73,10 +73,11 @@ html: ${GENERATED_SYNOPSIS}
 
 .PHONY: latexpdf
 latexpdf: ${GENERATED_SYNOPSIS}
+	@echo "Requires python3-sphinx, texlive-xetex and xindy"
 	$(SPHINXBUILD) -b latex $(ALLSPHINXOPTS) $(BUILDDIR)/latex
-	@echo "Running LaTeX files through pdflatex..."
+	@echo "Running LaTeX files through xelatex..."
 	$(MAKE) -C $(BUILDDIR)/latex all-pdf
-	@echo "pdflatex finished; the PDF files are in $(BUILDDIR)/latex."
+	@echo "xelatex finished; the PDF files are in $(BUILDDIR)/latex."
 
 .PHONY: epub3
 epub3: ${GENERATED_SYNOPSIS}

docs/conf.py

@@ -251,14 +251,24 @@ htmlhelp_basename = 'ProxmoxBackupdoc'
 
 # -- Options for LaTeX output ---------------------------------------------
 
+latex_engine = 'xelatex'
+
 latex_elements = {
+    'fontenc': '\\usepackage{fontspec}',
+
      # The paper size ('letterpaper' or 'a4paper').
      #
      'papersize': 'a4paper',
 
      # The font size ('10pt', '11pt' or '12pt').
      #
-     'pointsize': '12pt',
+     'pointsize': '10pt',
+
+    'fontpkg': r'''
+\setmainfont{DejaVu Serif}
+\setsansfont{DejaVu Sans}
+\setmonofont{DejaVu Sans Mono}
+''',
 
      # Additional stuff for the LaTeX preamble.
      #