title: Getting "Creation of service was not idempotent" with boto3 ECS. Why?
body: <p>I am making a call to <code>ecs.create_service</code> like this:</p>
  
  <pre><code>createServiceResponse = ecs.create_service(
  clientToken='abc123',
  cluster=options.cluster,
  serviceName=options.service,
  desiredCount=1,
  taskDefinition='relay:' + str(revision),
  role='ecsServiceRole',
  loadBalancers=[
      {
          'loadBalancerName': options.elb,
          'containerName': 'relay',
          'containerPort': 8080
      }
  ]
  )
  </code></pre>
  
  <p>Note that the value in clientToken is <code>abc123</code> at the moment, but I've tried all sorts of different strings. This document says I need to supply it to ensure idempotency (<a href="http://boto3.readthedocs.org/en/latest/reference/services/ecs.html" rel="noreferrer">http://boto3.readthedocs.org/en/latest/reference/services/ecs.html</a>) however I keep getting this error:</p>
  
  <pre class="lang-none prettyprint-override"><code>Traceback (most recent call last):
    File "./deploy.py", line 103, in &lt;module&gt;
      'containerPort': 8080
    File "/usr/local/lib/python2.7/site-packages/botocore/client.py", line 301, in _api_call
    return self._make_api_call(operation_name, kwargs)
    File "/usr/local/lib/python2.7/site-packages/botocore/client.py", line 386, in _make_api_call
     raise ClientError(parsed_response, operation_name)
  botocore.exceptions.ClientError: An error occurred     (InvalidParameterException) when calling the CreateService operation: Creation of service was not idempotent.
  </code></pre>
  
  <p>Why ?</p>