test-unit-ruby-core-1.0.15: Ruby 2.6 fails in CI, undefined method 'bind_call'

[olleolleolle]

Example CI test failure from Ruby 2.6:

| /home/runner/work/timeout/timeout/vendor/bundle/ruby/2.6.0/gems/test-unit-ruby-core-1.0.15/lib/core_assertions.rb:330:in block in separated_runner': undefined method bind_call' for #<UnboundMethod: Integer#to_s> (NoMethodError)

[eregon]

example log: https://github.com/ruby/timeout/actions/runs/31351472087/job/93343044877?pr=115

[eregon]

This is a failure caused by https://github.com/ruby/test-unit-ruby-core, could you report it there?

[olleolleolle]

ruby/test-unit-ruby-core#27 someone got there before me! EDIT: Ah, that was another thing.

I have now reported that issue:
ruby/test-unit-ruby-core#28