Impacted versions: ODOO 10

Problem.
If i print a invoice with a negative amount, the pdf shows a vertical bar instead of a minus symbol.
![image](https://cloud.githubusercontent.com/assets/28800797/26237253/b07fadb0-3c74-11e7-86c2-c8688d82b5a5.png)

I have tried to install a new pdf reader, but with no result.
return int(bool(self.eval(expr, qwebcontext)))
    def render(self, cr, uid, id_or_xml_id, qwebcontext=None, loader=None, context=None):
        """ render(cr, uid, id_or_xml_id, qwebcontext=None, loader=None, context=None)
        Renders the template specified by the provided template name
        :param qwebcontext: context for rendering the template
        :type qwebcontext: dict or :class:`QWebContext` instance
        :param loader: if ``qwebcontext`` is a dict, loader set into the
                       context instantiated for rendering
        """
        if qwebcontext is None:
            qwebcontext = {}
        if not isinstance(qwebcontext, QWebContext):
            qwebcontext = QWebContext(cr, uid, qwebcontext, loader=loader, context=context)
        qwebcontext['__template__'] = id_or_xml_id
        stack = qwebcontext.get('__stack__', [])
        if stack:
            qwebcontext['__caller__'] = stack[-1]
        stack.append(id_or_xml_id)
        qwebcontext['__stack__'] = stack
        qwebcontext['xmlid'] = str(stack[0]) 
        element = self.get_template(id_or_xml_id, qwebcontext)
        element.attrib.pop("name", False)
        return self.render_node(element, qwebcontext, generated_attributes=qwebcontext.pop('generated_attributes', ''))
    def render_node(self, element, qwebcontext, generated_attributes=''):