PDF not generated

[saturnflyer]

This likely has more to do with my system than a problem with quarto but my PDFs are not being created.
Here's what I'm seeing:

pandoc --table-of-contents --standalone build/master/master.xhtml | xmlstarlet sel -I -t -c "//*[@id='TOC']" > build/prince/toc.xml
Attempt to load network entity http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd
rake aborted!
Command failed with status (1): [pandoc --table-of-contents --standalone bu...]
/Users/jim/Projects/quarto/lib/quarto/prince.rb:62:in `block in define_tasks'
/Users/jim/.gem/ruby/2.2.0/bin/ruby_executable_hooks:15:in `eval'
/Users/jim/.gem/ruby/2.2.0/bin/ruby_executable_hooks:15:in `<main>'
Tasks: TOP => deliverables => build/deliverables/ruby-dsl-handbook.pdf => build/master/prince_master.xhtml => build/prince/toc.xml

Here's my relevant config:

require 'quarto/tasks'

require 'quarto'

Quarto.configure do |config|
  config.author      = "Jim Gay"
  config.title       = "Ruby DSL Handbook"
  config.name        = 'ruby-dsl-handbook'

  # config.stylesheets.clear
  config.metadata = true

  # config.use :git
  config.use :markdown
  # config.use :doc_raptor
  config.use :pandoc_epub
  config.use :epubcheck
  config.use :kindlegen
  config.use :bundle
  config.use :site
  config.use :prince
  config.source_files = %w[ files listed here ]
  config.bitmap_cover_image              = "images/cover-large.png"
  config.vector_cover_image              = "images/cover.svg"
  config.stylesheets.cover_color         = "#222"
  config.stylesheets.heading_font        = '"PT Sans", sans-serif'
  config.stylesheets.font                = '"PT Serif", serif

What can I do to debug this?

[saturnflyer]

I'm on OS X and using homebrew. My prince install wasn't linked properly. After fixing it (I think) the error changes:

create build/master/prince_master.xhtml from build/master/master.xhtml
rake aborted!
NoMethodError: undefined method `first_element_child' for nil:NilClass
/Users/jim/Projects/quarto/lib/quarto/prince.rb:134:in `create_prince_master_file'
/Users/jim/Projects/quarto/lib/quarto/prince.rb:50:in `block in define_tasks'
/Users/jim/.gem/ruby/2.2.0/bin/ruby_executable_hooks:15:in `eval'
/Users/jim/.gem/ruby/2.2.0/bin/ruby_executable_hooks:15:in `<main>'

The toc.xml file generated in build/prince is completely blank.

[saturnflyer]

The following command is operating on a blank toc file.

pandoc --table-of-contents --standalone build/master/master.xhtml | xmlstarlet sel -I -t -c "//*[@id='TOC']" > build/prince/toc.xml

When I looked at the contents of the generate xml file, there was not element with an id of "TOC"

pandoc --table-of-contents --standalone build/master/master.xhtml | less

I'm looking into pandoc to find out why it's not creating that element. I'm not sure if there's something that I need to do or if pandoc makes assumptions and creates the TOC automatically