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.
openerp/addons/base/ir/ir_qweb.py
inner = self.eval_str(template_attributes["raw"], qwebcontext)
        return self.render_element(element, template_attributes, generated_attributes, qwebcontext, inner)
    def render_tag_esc(self, element, template_attributes, generated_attributes, qwebcontext):
        options = json.loads(template_attributes.get('esc-options') or '{}')
        widget = self.get_widget_for(options.get('widget'))
        inner = widget.format(template_attributes['esc'], options, qwebcontext)
        return self.render_element(element, template_attributes, generated_attributes, qwebcontext, inner)
    def _iterate(self, iterable):
        if isinstance (iterable, collections.Mapping):
            return iterable.iteritems()
        return itertools.izip(*itertools.tee(iterable))
    def render_tag_foreach(self, element, template_attributes, generated_attributes, qwebcontext):
        expr = template_attributes["foreach"]
        enum = self.eval_object(expr, qwebcontext)
        if enum is None:
            template = qwebcontext.get('__template__')
            raise QWebException("foreach enumerator %r is not defined while rendering template %r" % (expr, template), template=template)
        if isinstance(enum, int):
            enum = range(enum)
        varname = template_attributes['as'].replace('.', '_')
        copy_qwebcontext = qwebcontext.copy()
        size = None
        if isinstance(enum, collections.Sized):