Rendering a PDF emits warning with 1.5.8

[robertpanzer]

When rendering a PDF with the latest 1.5.8 I get a warning:

Okt 29, 2018 6:02:24 PM <script> (root)
WARNUNG: gem 'concurrent-ruby' is not installed. This gem is recommended when registering custom converters.

Apparently I forgot to add this gem.

@mojavelinux Is this critical? Should I prepare a 1.5.8.1 release?

[mojavelinux]

I forgot to give you a heads up about this. Asciidoctor 1.5.8 no longer uses thread_safe. That gem has been deprecated. It now uses concurrent-ruby. It provides the same functionality, but does not offer a compatible API. For details, see asciidoctor/asciidoctor#2822.

[robertpanzer]

So do you think we need a new release?

I guess we will have to keep thread_safe in the asciidoctorj.jar because asciidoctorj-pdf relies on it being available.

[mojavelinux]

So do you think we need a new release?

Yes, I think it's worth it.

I guess we will have to keep thread_safe in the asciidoctorj.jar because asciidoctorj-pdf relies on it being available.

Correct. Both are currently needed.

[robertpanzer]

Fixed with 1.5.8.1