I think this causes the CI failure:
```
1) operator matchers unsupported operators raises an appropriate error for should_not !~ expected
     Failure/Error: expect {
       expected Exception with message matching /does not support `should_not !~ expected`.  Use `should =~ expected`/, got #<ArgumentError: wrong number of arguments (1 for 0)> with backtrace:
         # ./lib/rspec/matchers/built_in/operators.rb:58:in `block in use_custom_matcher_or_delegate'
```
```
./lib/rspec/expectations/fail_with.rb:33:in `fail_with'
     ./lib/rspec/expectations/handler.rb:38:in `handle_failure'
     ./lib/rspec/expectations/handler.rb:49:in `handle_matcher'
     ./lib/rspec/expectations/expectation_target.rb:54:in `to'
     ./lib/rspec/expectations/expectation_target.rb:87:in `to'
     ./spec/rspec/matchers/built_in/operators_spec.rb:70:in `block (3 levels) in <top (required)>'
```
https://travis-ci.org/rspec/rspec-expectations/jobs/24899893