class Google::Auth::ServiceAccountCredentials

def apply_self_signed_jwt! a_hash
  # Use the ServiceAccountJwtHeaderCredentials using the same cred values
  cred_json = {
    private_key: @signing_key.to_s,
    client_email: @issuer,
    project_id: @project_id,
    quota_project_id: @quota_project_id
  }
  key_io = StringIO.new MultiJson.dump(cred_json)
  alt = ServiceAccountJwtHeaderCredentials.make_creds json_key_io: key_io, scope: scope
  alt.logger = logger
  alt.apply! a_hash
end