[iam] flake: keyerror

[tmatsuo]

build

log

Traceback (most recent call last):
  File "/workspace/iam/api-client/grantable_roles_test.py", line 23, in test_service_accounts
    grantable_roles.view_grantable_roles(resource)
  File "/workspace/iam/api-client/grantable_roles.py", line 40, in view_grantable_roles
    print('Description: ' + role['description'])
KeyError: 'description'