Strange failure

[RDIL]

Got the following on a CircleCI build:

Running ["LinkCheck", "ImageCheck", "ScriptCheck", "OpenGraphCheck", "FaviconCheck"] on ["./_site"] on *.html... 


rake aborted!
ArgumentError: invalid byte sequence in US-ASCII
/usr/local/bundle/gems/html-proofer-3.10.2/lib/html-proofer/utils.rb:32:in `gsub'
/usr/local/bundle/gems/html-proofer-3.10.2/lib/html-proofer/utils.rb:32:in `clean_content'
/usr/local/bundle/gems/html-proofer-3.10.2/lib/html-proofer/utils.rb:16:in `create_nokogiri'
/usr/local/bundle/gems/html-proofer-3.10.2/lib/html-proofer/runner.rb:95:in `check_path'
/usr/local/bundle/gems/html-proofer-3.10.2/lib/html-proofer/runner.rb:87:in `block in process_files'
/usr/local/bundle/gems/html-proofer-3.10.2/lib/html-proofer/runner.rb:87:in `map'
/usr/local/bundle/gems/html-proofer-3.10.2/lib/html-proofer/runner.rb:87:in `process_files'
/usr/local/bundle/gems/html-proofer-3.10.2/lib/html-proofer/runner.rb:68:in `check_files'
/usr/local/bundle/gems/html-proofer-3.10.2/lib/html-proofer/runner.rb:40:in `run'
/root/repo/Rakefile:5:in `block in <top (required)>'
/usr/local/bundle/gems/rake-12.3.2/exe/rake:27:in `<top (required)>'
/usr/local/bundle/gems/bundler-2.0.1/lib/bundler/cli/exec.rb:74:in `load'
/usr/local/bundle/gems/bundler-2.0.1/lib/bundler/cli/exec.rb:74:in `kernel_load'
/usr/local/bundle/gems/bundler-2.0.1/lib/bundler/cli/exec.rb:28:in `run'
/usr/local/bundle/gems/bundler-2.0.1/lib/bundler/cli.rb:463:in `exec'
/usr/local/bundle/gems/bundler-2.0.1/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
/usr/local/bundle/gems/bundler-2.0.1/lib/bundler/vendor/thor/lib/thor/invocation.rb:126:in `invoke_command'
/usr/local/bundle/gems/bundler-2.0.1/lib/bundler/vendor/thor/lib/thor.rb:387:in `dispatch'
/usr/local/bundle/gems/bundler-2.0.1/lib/bundler/cli.rb:27:in `dispatch'
/usr/local/bundle/gems/bundler-2.0.1/lib/bundler/vendor/thor/lib/thor/base.rb:466:in `start'
/usr/local/bundle/gems/bundler-2.0.1/lib/bundler/cli.rb:18:in `start'
/usr/local/bundle/gems/bundler-2.0.1/exe/bundle:30:in `block in <top (required)>'
/usr/local/bundle/gems/bundler-2.0.1/lib/bundler/friendly_errors.rb:124:in `with_friendly_errors'
/usr/local/bundle/gems/bundler-2.0.1/exe/bundle:22:in `<top (required)>'
/usr/local/bundle/gems/bundler-2.0.1/exe/bundler:4:in `load'
/usr/local/bundle/gems/bundler-2.0.1/exe/bundler:4:in `<top (required)>'
/usr/local/bundle/bin/bundler:23:in `load'
/usr/local/bundle/bin/bundler:23:in `<main>'
Tasks: TOP => test
(See full trace by running task with --trace)
Exited with code 1

Rakefile:

require 'html-proofer'

task :test do
  options = { :assume_extension => true, :check_favicon => true, :check_opengraph => true }
  HTMLProofer.check_directory("./_site", options).run
end