title: Failed processing pyformat-parameters; 'MySQLConverter' object has no attribute '_list_to_mysql'
body: <p>I have a python script which everytime a wait_for_page call is made it writes the time it took to wait for the page to a database. The query is below:</p>
  
  <pre><code>    conn = mysql.connector.connect(**config)
      connect = conn.cursor()
      params = {'build': self.tc.tag, 'page': unicode(self), 'object_id': self.object_id, 'page_header':
                self.page_header, 'interval': t.interval, 'timestamp': timestamp}
      query = u'INSERT INTO page_load_times (build, page, object_id, page_header, elapsed_time, date_run) ' \
              'VALUES (%(build)s, %(page)s, %(object_id)s, %(page_header)s, %(interval)s, %(timestamp)s)'
      connect.execute(query, params)
      conn.commit()
      conn.close()
  </code></pre>
  
  <p>Occasionally, when this runs, I get an error which says:</p>
  
  <pre><code> "Failed processing pyformat-parameters; %s" % err)
   ProgrammingError: Failed processing pyformat-parameters; 'MySQLConverter' 
   object has no attribute '_list_to_mysql'
  </code></pre>
  
  <p>I know what is causing this, just uncertain how to go about fixing it. The <code>'page': unicode(self)</code> param occasionally gets a list as a result. </p>
  
  <p>In an attempt to fix this, I tweaked the above script to extract the list into a string, with the following:</p>
  
  <pre><code>    page_list = u'{}'.format(self)
      page_results = "('%s')" % "','".join(page_list)
      params = {'build': self.tc.tag, 'page': page_results, 'object_id': self.object_id, 'page_header':
                self.page_header, 'interval': t.interval, 'timestamp': timestamp}
  </code></pre>
  
  <p>When I run this, the error I am getting now is that the data is too long for the field. I debug it, to find that my page results has each character parsed out individually looking like so:</p>
  
  <pre><code>u'(\\'A\\',\\'p\\',\\'p\\',\\'M\\',\\'a\\',\\'i\\',\\'n\\',\\'M\\',\\'e\\',\\'n\\',\\'u\\',\\':\\',\\' \\',\\'N\\',\\'o\\',\\'n\\',\\'e\\')'
  </code></pre>