title: TypeError: object of type 'bool' has no len() - Odoo v9
body: <p>I'm trying to connect to a webservice through an Odoov9 module.</p>
  
  <p>This is my class:</p>
  
  <pre><code>class invoice(models.Model):
  _inherit = "account.invoice"
  
  @api.multi
  def send_xml_file(self):
      # haciendolo para efacturadelsur solamente por ahora
      host = 'https://www.efacturadelsur.cl'
      post = '/ws/DTE.asmx' # HTTP/1.1
      url = host + post
      _logger.info('URL to be used %s' % url)
      # client = Client(url)
      # _logger.info(client)
      _logger.info('len (como viene): %s' % len(self.sii_xml_request))
  
      response = pool.urlopen('POST', url, headers={
          'Content-Type': 'application/soap+xml',
          'charset': 'utf-8',
          'Content-Length': len(
              self.sii_xml_request)}, body=self.sii_xml_request)
  
      _logger.info(response.status)
      _logger.info(response.data)
      self.sii_xml_response = response.data
      self.sii_result = 'Enviado'
  </code></pre>
  
  <p>But everytime it parses the code to connect to the server, it throws this error:</p>
  
  <pre><code>Odoo Server Error
  
  Traceback (most recent call last):
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/http.py", line 646, in _handle_exception
  return super(JsonRequest, self)._handle_exception(exception)
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/http.py", line 683, in dispatch
  result = self._call_function(**self.params)
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/http.py", line 319, in _call_function
  return checked_call(self.db, *args, **kwargs)
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/service/model.py", line 118, in wrapper
  return f(dbname, *args, **kwargs)
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/http.py", line 312, in checked_call
  result = self.endpoint(*a, **kw)
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/http.py", line 962, in __call__
  return self.method(*args, **kw)
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/http.py", line 512, in response_wrap
  response = f(*args, **kw)
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/addons/web/controllers/main.py", line 901, in call_button
  action = self._call_kw(model, method, args, {})
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/addons/web/controllers/main.py", line 889, in _call_kw
  return getattr(request.registry.get(model), method)(request.cr, request.uid, *args, **kwargs)
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/api.py", line 250, in wrapper
  return old_api(self, *args, **kwargs)
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/api.py", line 381, in old_api
  result = method(recs, *args, **kwargs)
  File "/home/kristian/odoov9/odoo-9.0c-20160712/openerp/addons/l10n_cl_dte/models/invoice.py", line 102, in send_xml_file
  _logger.info('len (como viene): %s' % len(self.sii_xml_request))
  TypeError: object of type 'bool' has no len()
  </code></pre>
  
  <p>The error is on this line </p>
  
  <p><code>_logger.info('URL to be used %s' % url)
     # client = Client(url)
     # _logger.info(client)
     _logger.info('len (como viene): %s' % len(self.sii_xml_request))</code></p>
  
  <p>I've searched through SO, and it seems to be related to parenthesis, but I'm still not really sure.</p>
  
  <p>Any ideas on this?</p>
  
  <p>Thanks in advance!</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>This is the code that sets it:</p>
  
  <pre><code>    sii_xml_request = fields.Text(
      string='SII XML Request',
      copy=False,
      )
  </code></pre>