[BUG] RELATIVE refs could not be loaded

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?

Description

After the latest version of the OpenAPI Generator was released: 5.2.0, a new bug was introduced regarding relative $refs: during generation the following error occurs:

[main] WARN  io.swagger.v3.parser.OpenAPIV3Parser - Exception while resolving:
java.lang.RuntimeException: Unable to load RELATIVE ref: ./specs/my_spec.yaml path: /specs/spec_path

This behaviour is only seen in the latest released version, previously it was working correctly. I've looked through the CHANGELOG document but couldn't find an entry that could have introduced this problem.

openapi-generator version

5.2.0

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: MyExampleSpec
  description: >-
paths: {}
components:
  schemas:
    MyExampleSchema:
      description: >-
      properties:
        id:
          description: The id of MyExampleSchema.
          type: string
        message:
          description: The message of MyExampleSchema.
          $ref: ../specs/MySchemas.yaml#/components/schemas/Message

Generation Details

Steps to reproduce

1. Build the OpenAPI Generator.
2. Run one of the generators ( I've tested it with PowerShell and Python) with the provided yaml using the following command:

java openapi-generator-cli-5.2.0.jar generate -g powershell -i "myOpenAPISpec.yaml" --global-property

3. Observe the errors that occur which should match the mentioned error message above.

Related issues/PRs

none

Suggest a fix

Currently no fix suggestion can be provided. I'll try to find the root cause of the issue and then think about what kind of fix can be added.

Build OpenAPI Generator and run the CLI generate command with the supplied YAML and the PowerShell or Python generator. Compare version 5.2.0 with the previously working version and trace the relative $ref loading error; done means the example resolves without the reported exception.