title: The correct why to debug dask.dataframe.to_parquet
body: <p>I've seen that there are some issues with the type of column objects when running the <code>to_parquet</code> function.  I'm running dask version 15.1 .</p>
  
  <p>I've explicitly converted my columns using the <a href="http://dask.pydata.org/en/latest/dataframe-api.html#dask.dataframe.DataFrame.astype" rel="nofollow noreferrer">astype(object)</a>, which helped with some columns but not all.<br>
  I'm getting the following error -  <code>TypeError: bad argument type for built-in operation</code>.<br>
  After adding the <code>object_encoding='utf-8</code> parameter I'm getting the following error - <code>TypeError: expected list of bytes</code> .</p>
  
  <p>What would be the best way to debug this issue?<br>
  BTW- My dataset has Hebrew characters.</p>
  
  <p>Thx</p>