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.field.text'
    _inherit = 'ir.qweb.field'
    def value_to_html(self, cr, uid, value, field, options=None, context=None):
        """
        Escapes the value and converts newlines to br. This is bullshit.
        """
        if not value: return ''
        return nl2br(value, options=options)
class SelectionConverter(osv.AbstractModel):
    _name = 'ir.qweb.field.selection'
    _inherit = 'ir.qweb.field'
    def record_to_html(self, cr, uid, field_name, record, options=None, context=None):
        value = record[field_name]
        if not value: return ''
        field = record._fields[field_name]
        selection = dict(field.get_description(record.env)['selection'])
        return self.value_to_html(
            cr, uid, selection[value], field, options=options)
class ManyToOneConverter(osv.AbstractModel):
    _name = 'ir.qweb.field.many2one'
    _inherit = 'ir.qweb.field'
    def record_to_html(self, cr, uid, field_name, record, options=None, context=None):
        if not record:
            return ''
        [read] = record.read([field_name])
        if not read[field_name]: return ''
        _, value = read[field_name]
        return nl2br(value, options=options)
class HTMLConverter(osv.AbstractModel):