title: Google Drive API insert Excel file works, but update doesn't
body: <p>I'm using the Google Drive API and have found that I can access a Google spreadsheet's metadata and download it in 'xls' and 'xlsx' formats just fine. I've also been able to use the API to insert (add new) Excel files and convert them to Google spreadsheets. However, no matter what I do, <strong>I get 500 errors trying to update a Google Spreadsheet with an Excel file</strong>. Is this unsupported?</p>
  
  <p>I'm using the python client library and examples for insert and upload:</p>
  
  <ul>
  <li><a href="https://developers.google.com/drive/v2/reference/files/insert#examples" rel="nofollow">https://developers.google.com/drive/v2/reference/files/insert#examples</a> </li>
  <li><a href="https://developers.google.com/drive/v2/reference/files/update#examples" rel="nofollow">https://developers.google.com/drive/v2/reference/files/update#examples</a></li>
  </ul>
  
  <p>I have a single script where auth happens fine, I build a service just fine, and with the example code above modified only to add the parameter <code>convert=True</code> I can call:</p>
  
  
  
  <pre><code>insert_file(service, title="test", description="description", parent_id=None,
              mime_type="application/vnd.ms-excel", filename="test.xls")
  </code></pre>
  
  <ul>
  <li>Success. I can open this new spreadsheet on Google Drive, which has been converted.</li>
  <li>variable <code>file_id</code> below is set to the file_id returned in the JSON from the successful file creation. I can use this id to get the new file's metadata again, download the file, etc.</li>
  </ul>
  
  <p>then</p>
  
  <pre><code>update_file(service, file_id, title="modified test",
              description="modified description",
              mime_type="application/vnd.ms-excel", filename="test2.xls",
              new_revision=True)
  </code></pre>
  
  <ul>
  <li>Fails with error 500</li>
  </ul>
  
  <p>I've tried with <code>new_revision=False</code>, not changing any of the metadata, and setting <code>resumable=False</code> in the <code>MediaFileUpload()</code> object creation.</p>