Fix Ruby 2.7 keyword deprecation warning in validators/coerce

[K0H205]

Fix these deprecation warnings

grape/lib/grape/validations/validators/coerce.rb:21: warning: Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call
grape/lib/grape/validations/validators/base.rb:16: warning: The called method `initialize' is defined here

[dblock]

Is there any way we can fail CI when we have these warnings? Maybe a Danger plugin?

[grape-bot]

	1 Warning
⚠️	There’re library changes, but not tests. That’s OK as long as you’re refactoring existing code.

Generated by 🚫 danger

[K0H205]

Is there any way we can fail CI when we have these warnings?

I can't suggest enough ways to make CI fail with ruby warnings.

[eregon]

Is there any way we can fail CI when we have these warnings? Maybe a Danger plugin?

The warning gem could be use to turn warnings into exceptions, that might be one way.

[dblock]

@eregon You'll be my hero if you can make it work.

[dblock]

Btw, I had tried in spec_helper to override warn, which worked. The problem was that I couldn't have both specs that expect warnings and always fail on unexpected warnings without some nasty hack. I might retry this.

[eregon]

That gem seems to allow filtering warnings like :keyword_separation so that might be helpful.