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.
self.string = string
    def __html__(self):
        return self.string
    def __str__(self):
        s = self.string
        if isinstance(s, unicode):
            return s.encode('utf-8')
        return s
    def __unicode__(self):
        s = self.string
        if isinstance(s, str):
            return s.decode('utf-8')
        return s
def nl2br(string, options=None):
    """ Converts newlines to HTML linebreaks in ``string``. Automatically
    escapes content unless options['html-escape'] is set to False, and returns
    the result wrapped in an HTMLSafe object.
    :param str string:
    :param dict options:
    :rtype: HTMLSafe
    """
    if options is None: options = {}
    if options.get('html-escape', True):
        string = escape(string)
    return HTMLSafe(string.replace('\n', '<br>\n'))
def get_field_type(field, options):
    """ Gets a t-field's effective type from the field definition and its options """
    return options.get('widget', field.type)
class AssetError(Exception):