[DRE-maint] Bug#888170: ruby-redcloth: FTBFS on ruby2.5: undefined method `load_documents' for Psych:Module

[Chris West (Faux)]

Source: ruby-redcloth
Version: 4.3.2-2
Severity: important
User: debian-ruby at lists.debian.org
Usertags: ruby2.5

Dear Maintainer,

This package fails to build against ruby2.5. Soon, there will
be a transition to ruby2.5, and this package will FTBFS in sid.

There may be some details on the wiki about common problems:
https://wiki.debian.org/Teams/Ruby/Ruby25Transition

Build log excerpt:

Finished in 1.43 seconds (files took 0.86964 seconds to load)
5797 examples, 0 failures

/usr/bin/ruby2.5 /usr/bin/gem2deb-test-runner

┌──────────────────────────────────────────────────────────────────────────────┐
│ Run tests for ruby2.5 from debian/ruby-tests.rake                            │
└──────────────────────────────────────────────────────────────────────────────┘

RUBYLIB=/build/ruby-redcloth-4.3.2/debian/ruby-redcloth/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.5.0:/build/ruby-redcloth-4.3.2/debian/ruby-redcloth/usr/lib/ruby/vendor_ruby:. GEM_PATH=debian/ruby-redcloth/usr/share/rubygems-integration/2.5.0:/root/.gem/ruby/2.5.0:/var/lib/gems/2.5.0:/usr/lib/x86_64-linux-gnu/rubygems-integration/2.5.0:/usr/share/rubygems-integration/2.5.0:/usr/share/rubygems-integration/all ruby2.5 -S rake -f debian/ruby-tests.rake
/usr/bin/ruby2.5 /usr/bin/rspec --pattern ./spec/\*\*/\*_spec.rb --format documentation
/build/ruby-redcloth-4.3.2/spec/spec_helper.rb:29:in `block in fixtures': undefined method `load_documents' for Psych:Module (NoMethodError)
Did you mean?  load_stream
	from /build/ruby-redcloth-4.3.2/spec/spec_helper.rb:26:in `each'
	from /build/ruby-redcloth-4.3.2/spec/spec_helper.rb:26:in `fixtures'
	from /build/ruby-redcloth-4.3.2/spec/spec_helper.rb:9:in `examples_from_yaml'
	from /build/ruby-redcloth-4.3.2/spec/formatters/class_filtered_html_spec.rb:4:in `block in <top (required)>'
	from /usr/lib/ruby/vendor_ruby/rspec/core/example_group.rb:385:in `module_exec'
	from /usr/lib/ruby/vendor_ruby/rspec/core/example_group.rb:385:in `subclass'
	from /usr/lib/ruby/vendor_ruby/rspec/core/example_group.rb:258:in `block in define_example_group_method'
	from /usr/lib/ruby/vendor_ruby/rspec/core/dsl.rb:43:in `block in expose_example_group_alias'
	from /usr/lib/ruby/vendor_ruby/rspec/core/dsl.rb:84:in `block (2 levels) in expose_example_group_alias_globally'
	from /build/ruby-redcloth-4.3.2/spec/formatters/class_filtered_html_spec.rb:3:in `<top (required)>'
	from /usr/lib/ruby/vendor_ruby/rspec/core/configuration.rb:1435:in `load'
	from /usr/lib/ruby/vendor_ruby/rspec/core/configuration.rb:1435:in `block in load_spec_files'
	from /usr/lib/ruby/vendor_ruby/rspec/core/configuration.rb:1433:in `each'
	from /usr/lib/ruby/vendor_ruby/rspec/core/configuration.rb:1433:in `load_spec_files'
	from /usr/lib/ruby/vendor_ruby/rspec/core/runner.rb:100:in `setup'
	from /usr/lib/ruby/vendor_ruby/rspec/core/runner.rb:86:in `run'
	from /usr/lib/ruby/vendor_ruby/rspec/core/runner.rb:71:in `run'
	from /usr/lib/ruby/vendor_ruby/rspec/core/runner.rb:45:in `invoke'
	from /usr/bin/rspec:4:in `<main>'
/usr/bin/ruby2.5 /usr/bin/rspec --pattern ./spec/\*\*/\*_spec.rb --format documentation failed
ERROR: Test "ruby2.5" failed. Exiting.
dh_auto_install: dh_ruby --install /build/ruby-redcloth-4.3.2/debian/ruby-redcloth returned exit code 1
make: *** [binary] Error 1
debian/rules:15: recipe for target 'binary' failed
dpkg-buildpackage: error: debian/rules binary subprocess returned exit status 2

Full build log:
https://rbuild.fau.xxx/2018-01-23/ruby-redcloth.log

Please fix it!

Cheers,
Chris.