ACM Cert lookup fails with KeyError

[hjacobs]

Generating Cloud Formation template.. EXCEPTION OCCURRED: 'Serial'
Unknown Error: 'Serial'.
Please create an issue with the content of /tmp/senza-traceback-078eseqg

$ cat /tmp/senza-traceback-078eseqg
Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/senza/error_handling.py", line 69, in __call__
    self.function(*args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/click/core.py", line 716, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/click/core.py", line 696, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python3.5/dist-packages/click/core.py", line 1060, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python3.5/dist-packages/click/core.py", line 889, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python3.5/dist-packages/click/core.py", line 534, in invoke
    return callback(*args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/senza/cli.py", line 555, in create
    data = create_cf_template(definition, region, version, parameter, force, parameter_file)
  File "/usr/local/lib/python3.5/dist-packages/senza/cli.py", line 638, in create_cf_template
    data = evaluate(definition.copy(), args, account_info, force)
  File "/usr/local/lib/python3.5/dist-packages/senza/cli.py", line 239, in evaluate
    definition = componentfn(definition, configuration, args, info, force, account_info)
  File "/usr/local/lib/python3.5/dist-packages/senza/components/weighted_dns_elastic_load_balancer.py", line 29, in component_weighted_dns_elastic_load_balancer
    return component_elastic_load_balancer(definition, configuration, args, info, force, account_info)
  File "/usr/local/lib/python3.5/dist-packages/senza/components/elastic_load_balancer.py", line 110, in component_elastic_load_balancer
    listeners = configuration.get('Listeners') or get_listeners(subdomain, main_zone, configuration)
  File "/usr/local/lib/python3.5/dist-packages/senza/components/elastic_load_balancer.py", line 48, in get_listeners
    reverse=True)
  File "/usr/local/lib/python3.5/dist-packages/senza/manaus/acm.py", line 173, in get_certificates
    certificate = ACMCertificate.get_by_arn(arn)
  File "/usr/local/lib/python3.5/dist-packages/senza/manaus/acm.py", line 110, in get_by_arn
    return cls.from_boto_dict(certificate)
  File "/usr/local/lib/python3.5/dist-packages/senza/manaus/acm.py", line 83, in from_boto_dict
    serial = certificate['Serial']
KeyError: 'Serial'

The cert has status "'VALIDATION_TIMED_OUT" in the error case.