openapi-generator still uses methods that have been removed from urllib3
v2.6.0. The solution is as described in urllib3's changelog:
> Removed the HTTPResponse.getheaders() method in favor of
> HTTPResponse.headers. Removed the HTTPResponse.getheader(name,
> default) method in favor of HTTPResponse.headers.get(name, default).
> (#3622)
See https://urllib3.readthedocs.io/en/latest/changelog.htmlClose#22514