When running YaST RSpec tests under Ruby 2.2, many messages appear of the form

/usr/lib64/ruby/gems/2.2.0/gems/rspec-mocks-3.2.1/lib/rspec/mocks/argument_list_matcher.rb:84:
warning: Comparable#== will no more rescue exceptions of #<=> in the next
release.
/usr/lib64/ruby/gems/2.2.0/gems/rspec-mocks-3.2.1/lib/rspec/mocks/argument_list_matcher.rb:84:
warning: Return nil in #<=> if the comparison is inappropriate or avoid such
comparison.
/usr/lib64/ruby/gems/2.2.0/gems/rspec-support-3.2.2/lib/rspec/support/fuzzy_matcher.rb:15:
warning: Comparable#== will no more rescue exceptions of #<=> in the next
release.
/usr/lib64/ruby/gems/2.2.0/gems/rspec-support-3.2.2/lib/rspec/support/fuzzy_matcher.rb:15:
warning: Return nil in #<=> if the comparison is inappropriate or avoid such
comparison.

This is a result of a fix in the Ruby core library:
https://bugs.ruby-lang.org/issues/7688

It is trying to tell us that a "<=>" operation is raising an exception.
I have identified Yast::Path#<=> as one of the culprits: it assumes that the
`other` object is a Path too:
https://github.com/yast/yast-ruby-bindings/blob/7f6545d5185aa3d3d49d907b5df08c3859d9c83b/src/ruby/yast/path.rb#L47