requests/models.py
<<<<<<< SEARCH
            else:
                if data:
                    body = self._encode_params(data)
                    if isinstance(data, str) or isinstance(data, builtin_str) or hasattr(data, 'read'):
                        content_type = None
                    else:
                        content_type = 'application/x-www-form-urlencoded'
=======
            else:
                if data is not None:
                    body = self._encode_params(data)
                    if isinstance(data, str) or isinstance(data, builtin_str) or hasattr(data, 'read'):
                        content_type = None
                    else:
                        content_type = 'application/x-www-form-urlencoded'
>>>>>>> REPLACE
requests/models.py
<<<<<<< SEARCH
            self.prepare_content_length(body)

            # Add content-type if it wasn't explicitly provided.
            if (content_type) and (not 'content-type' in self.headers):
                self.headers['Content-Type'] = content_type
=======
            if body is not None or self.method not in ('GET', 'HEAD'):
                self.prepare_content_length(body)

            # Add content-type if it wasn't explicitly provided.
            if (content_type) and (not 'content-type' in self.headers):
                self.headers['Content-Type'] = content_type
>>>>>>> REPLACE