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.
_name = 'ir.qweb.widget.monetary'
    _inherit = 'ir.qweb.widget'
    def _format(self, inner, options, qwebcontext):
        inner = self.pool['ir.qweb'].eval(inner, qwebcontext)
        display = self.pool['ir.qweb'].eval_object(options['display_currency'], qwebcontext)
        fmt = "%.{0}f".format(display.decimal_places)
        lang_code = qwebcontext.context.get('lang') or 'en_US'
        formatted_amount = self.pool['res.lang'].format(
            qwebcontext.cr, qwebcontext.uid, [lang_code], fmt, inner, grouping=True, monetary=True
        ).replace(r' ', u'\N{NO-BREAK SPACE}').replace(r'-', u'\u2011')
        pre = post = u''
        if display.position == 'before':
            pre = u'{symbol}\N{NO-BREAK SPACE}'
        else:
            post = u'\N{NO-BREAK SPACE}{symbol}'
        return u'{pre}{0}{post}'.format(
            formatted_amount, pre=pre, post=post
        ).format(symbol=display.symbol,)
class HTMLSafe(object):
    """ HTMLSafe string wrapper, Werkzeug's escape() has special handling for
    objects with a ``__html__`` methods but AFAIK does not provide any such
    object.
    Wrapping a string in HTML will prevent its escaping
    """
    __slots__ = ['string']
    def __init__(self, string):