Failures in oneOf, anyOf, etc, are actually in the referenced schema

Reproduce the issue with the provided OpenAPI YAML and the shown Docker command, then trace how validation handles oneOf and anyOf references. The fix is done when an invalid referenced Dog schema produces an error at components.schemas.Dog rather than at the containing oneOf or requestBody.

If a schema is invalid, it will cause a oneOf to fail instead of failing on its own. I discovered this while thinking optional was a valid thing.

The below is valid except I've added optional to Dog. The failure is now On instance['paths']['/pets']['patch']['requestBody'] instead of the expected ['components']['schemas']['Dog'].

paths:
  /pets:
    patch:
      requestBody:
        content:
          application/json:
            schema:
              oneOf:
                - $ref: '#/components/schemas/Cat'
                - $ref: '#/components/schemas/Dog'
      responses:
        '200':
          description: Updated
          content:
            application/json:
              schema:
                oneOf:
                  - $ref: '#/components/schemas/Cat'
                  - $ref: '#/components/schemas/Dog'
components:
  schemas:
    Dog:
      type: object
      optional: [ "bark" ]
      properties:
        bark:
          type: boolean
        breed:
          type: string
          enum: [Dingo, Husky, Retriever, Shepherd]
    Cat:
      type: object
      properties:
        hunts:
          type: boolean
        age:
          type: integer

$ docker run -v $PWD/simple.yaml:/openapi.yaml --rm p1c2u/openapi-spec-validator /openapi.yaml
{'content': {'application/json': {'schema': {'oneOf': [{'$ref': '#/components/schemas/Cat', 'x-scope': ['file:///openapi.yaml']}, {'$ref':'#/components/schemas/Dog', 'x-scope': ['file:///openapi.yaml']}]}}}} is not valid under any of the given schemas

Failed validating 'oneOf' in schema['properties']['paths']['patternProperties']['^\\/']['patternProperties']['^(get|put|post|delete|options|head|patch|trace)$']['properties']['requestBody']:                             
    {'oneOf': [{'$ref': '#/definitions/RequestBody'},
               {'$ref': '#/definitions/Reference'}]}

On instance['paths']['/pets']['patch']['requestBody']:
    {'content': {'application/json': {'schema': {'oneOf': [{'$ref': '#/components/schemas/Cat',
                                                            'x-scope': ['file:///openapi.yaml']},
                                                           {'$ref': '#/components/schemas/Dog',
                                                            'x-scope': ['file:///openapi.yaml']}]}}}}