title: Why is PollingIntervalTest test_getlastupdate_no_change failing with the error “could not convert string to float” in Sonos Self-Test Suite
body: <p>I've run the Sonos Self-Test Suite <a href="http://musicpartners.sonos.com/?q=docs" rel="nofollow">available here</a> and everything passes except for this one error, and I'm not sure why:</p>
  
  <pre><code>Test case: PollingIntervalTest test_getlastupdate_no_change
  Instance messages: could not convert string to float
  
  ...more output...
  2016-02-23 09:43:40,834 [STOP] SONOS.sonos.workflow.fixture.PollingIntervalTest - could not convert string to float:
  2016-02-23 09:43:40,834 [STOP] SONOS.sonos.workflow.fixture.PollingIntervalTest - 1212827 PollingIntervalTest test_getlastupdate_no_change
  2016-02-23 09:43:40,836 [DEBUG] SONOS.sonos.workflow.fixture.PollingIntervalTest - [('../../sonos-1.1.0.dev_r208947-py2.7.egg/sonos/workflow/fixture.py', 2494, '_run_test_iteration', 'testMethod()'), ('/Users/rob/Dropbox/dev/projects/composed/sonos_downloads/sonos-selftest/smapi/content_workflow/getlastupdate.py', 40, 'test_getlastupdate_no_change', 'poll_interval = self.smapiservice.get_polling_interval()'), ('../../sonos-1.1.0.dev_r208947-py2.7.egg/sonos/smapi/smapiservice.py', 374, 'get_polling_interval', "pollinterval = self.config.getfloat('Polling Interval', 'interval')")]
  2016-02-23 09:43:40,836 [INFO] SONOS.sonos.workflow.fixture.PollingIntervalTest - -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -
  2016-02-23 09:43:40,836 [INFO] SONOS.sonos.workflow.result - End *test case* test_getlastupdate_no_change at Tuesday, February 23, 2016 09:43 AM
  </code></pre>
  
  <p>Here's what my service returns:</p>
  
  <pre><code>&lt;soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:tns="http://www.sonos.com/Services/1.1"&gt;
    &lt;soap:Body&gt;
      &lt;tns:getLastUpdateResponse&gt;
        &lt;getLastUpdateResult&gt;
          &lt;catalog&gt;2016-02-18 11:52:30&lt;/catalog&gt;
          &lt;favorites&gt;Rob-2016-02-18 12:01:00&lt;/favorites&gt;
          &lt;pollInterval&gt;30&lt;/pollInterval&gt;
       &lt;/getLastUpdateResult&gt;
     &lt;/tns:getLastUpdateResponse&gt;
    &lt;/soap:Body&gt;
  &lt;/soap:Envelope&gt;
  </code></pre>
  
  <p>It seems virtually identical to the <a href="http://musicpartners.sonos.com/node/87" rel="nofollow">sample response in the Sonos API docs</a>. You can see that pollInterval has no type information specified in the SOAP XML, so I'm struggling to see how this error is due to something I'm doing.</p>
  
  <p>Am I doing something wrong, or could this be a problem with the test suite itself?</p>