Buiding from git produces a container that doesn't work (for me)

[filbranden]

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I've been trying to build docker-github-pages from the Dockerfile on git, but when I try it, it produces a container that doesn't seem to work...

When I try to run jekyll build on it, I get this error:

$ docker run --rm -v $PWD:/usr/src/app myjekyll jekyll build
/usr/local/lib/ruby/gems/2.5.0/gems/bundler-1.16.3/lib/bundler/spec_set.rb:91:in `block in materialize': Could not find concurrent-ruby-1.0.5 in any of the sources (Bundler::GemNotFound)
	from /usr/local/lib/ruby/gems/2.5.0/gems/bundler-1.16.3/lib/bundler/spec_set.rb:85:in `map!'
	from /usr/local/lib/ruby/gems/2.5.0/gems/bundler-1.16.3/lib/bundler/spec_set.rb:85:in `materialize'
	from /usr/local/lib/ruby/gems/2.5.0/gems/bundler-1.16.3/lib/bundler/definition.rb:171:in `specs'
	from /usr/local/lib/ruby/gems/2.5.0/gems/bundler-1.16.3/lib/bundler/definition.rb:238:in `specs_for'
	from /usr/local/lib/ruby/gems/2.5.0/gems/bundler-1.16.3/lib/bundler/definition.rb:227:in `requested_specs'
	from /usr/local/lib/ruby/gems/2.5.0/gems/bundler-1.16.3/lib/bundler/runtime.rb:108:in `block in definition_method'
	from /usr/local/lib/ruby/gems/2.5.0/gems/bundler-1.16.3/lib/bundler/runtime.rb:20:in `setup'
	from /usr/local/lib/ruby/gems/2.5.0/gems/bundler-1.16.3/lib/bundler.rb:107:in `setup'
	from /usr/local/bundle/gems/jekyll-3.7.4/lib/jekyll/plugin_manager.rb:50:in `require_from_bundler'
	from /usr/local/bundle/gems/jekyll-3.7.4/exe/jekyll:11:in `<top (required)>'
	from /usr/local/bundle/bin/jekyll:23:in `load'
	from /usr/local/bundle/bin/jekyll:23:in `<main>'

The container was built with this command:

$ docker build --no-cache -t myjekyll . 2>&1 | tee docker-build.log

The build logs are saved in this gist.

Any ideas of why this is failing? How can this build be made more robust?

Thanks! Filipe