[Swift4] CI tests on master for Swift4 are failing

Created by: spacether

Bug Report Checklist

Have you provided a full/minimal spec to reproduce the issue?
Have you validated the input using an OpenAPI validator (example)?
What's the version of OpenAPI Generator used?
Have you search for related issues/PRs?
What's the actual output vs expected output?
[Optional] Bounty to sponsor the fix (example)

Description

CI tests on master for Swift4 are failing, disable them See an example failure here: https://app.bitrise.io/build/944341d1e6af689d#?tab=log

Suggest a fix

Comment out the test