Ruby 2.6 & 2.7 failing GoogleApplicationDefaultCredentialsTest

[cben]

Both on v4.y and master branches, I guess something changed in dependendencies (?), now always fails with same error:

GoogleApplicationDefaultCredentialsTest#test_token:
ArgumentError: mocked method :apply expects 1 arguments, got []
    /home/beni/kubeclient/lib/kubeclient/google_application_default_credentials.rb:28:in `token'
    /home/beni/kubeclient/test/test_google_application_default_credentials.rb:14:in `block in test_token'
    /home/beni/kubeclient/test/test_google_application_default_credentials.rb:13:in `test_token'

help wanted. 🙏