Reconfigure RSpec/PredicateMatcher for better expectation failure messages

[Earlopain]

This is something that has bothered me for a while. There is an rspec cop for this to enforce better failure messages. I changed the config an let RuboCop autocorrect.

Changed expectations would previously output messages like this:

     Failure/Error: expect(options_keys.include?(:aautocorrect)).to be(true)

       expected true
            got false

The new expectations print the actual vs expected value:

     Failure/Error: expect(options_keys).to include(:aautocorrect)

       expected [:autocorrect_all, :autocorrect] to include :aautocorrect
       Diff:
       @@ -1 +1 @@
       -[:aautocorrect]
       +[:autocorrect_all, :autocorrect]

The same improvement also applies to something like expect($stderr.string.include?("whatever).to be(true) or expect(foo.nil?).to be(true) (and probably more)

---

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• Added tests.
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[bbatsov]

Nice change, I like it. The output is much better, plus it reads better IMO.

[Earlopain]

Had to change some application code here: https://github.com/rubocop/rubocop/pull/13001/files#diff-fd0332e5689d0ab642df39f706a915663f5d8764d4fa4442d36a291b16de70fb

For some reason the test for that would fail only with rspec 4 if this returns nil instead of false.