When the content of ticket has break-lines and especial characters like (á, à, ã, é, í, ó, õ, ú and ç) the webservice returns:
['ERROR_JSON_PAYLOAD_INVALID', 'JSON payload seems not valid']
My code:
ticket = glpi.create('ticket', {'name': notificacao.titulo, 'content': pystache.render(notificacao.mensagem, result).replace('\r', ''), 'itilcategories_id': notificacao.categoria.id_categoria_glpi, 'requesttypes_id': 9, 'type': 1})