title: Boto EMR creation gives "Log Uri is not in the required format" error
body: <p>The following code gives the error message </p>
  
  <pre><code>EmrResponseError: EmrResponseError: 400 Bad Request &lt;ErrorResponse xmlns="http://elasticmapreduce.amazonaws.com/doc/2009-03-31"&gt;   &lt;Error&gt;
      &lt;Type&gt;Sender&lt;/Type&gt;
      &lt;Code&gt;ValidationError&lt;/Code&gt;
      &lt;Message&gt;Log Uri is not in the required format&lt;/Message&gt;   &lt;/Error&gt;   &lt;RequestId&gt;1c3d0221-4420-11e4-a09e-5113f30a0036&lt;/RequestId&gt; &lt;/ErrorResponse&gt;
  </code></pre>
  
  <p>no matter sort of S3 URI I try. I've tried a trailing slash, s3n:// s3:// and all other combinations with no luck.</p>
  
  <p>Here's the code:</p>
  
  <pre><code>import boto.emr
  
  conn = boto.emr.connect_to_region('us-east-1')
  
  job_parameters = {"log_uri":"s3n://shadoop/logs/new-log",
          "ec2_keyname":"XXXXXX",
          "availability_zone":"us-east-1e",
          "master_instance_type":"m1-medium",
          "slave_instance_type":"m1-medium",
          "num_instances":"2",
          "keep_alive":"True",
          "enable_debugging":"True",
          "hadoop_version":"2.4.0",
          "ami_version":"3.1.0",
          "visible_to_all_users":"True"
      }
  jobid = conn.run_jobflow("test_cluster",job_parameters)
  </code></pre>