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.
_model = 'test_converter.monetary'
    def setUp(self):
        super(TestCurrencyExport, self).setUp()
        self.Currency = self.registry('res.currency')
        self.base = self.create(self.Currency, name="Source", symbol=u'source')
    def create(self, model, context=None, **values):
        return model.browse(
            self.cr, self.uid,
            model.create(self.cr, self.uid, values, context=context),
            context=context)
    def convert(self, obj, dest):
        converter = self.registry('ir.qweb.field.monetary')
        options = {
            'widget': 'monetary',
            'display_currency': 'c2'
        }
        context = dict(inherit_branding=True)
        converted = converter.to_html(
            self.cr, self.uid, 'value', obj, options,
            etree.Element('span'),
            {'field': 'obj.value', 'field-options': json.dumps(options)},
            '', ir_qweb.QWebContext(self.cr, self.uid, {'obj': obj, 'c2': dest, }),
            context=context,
        )
        return converted
    def test_currency_post(self):