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
def minify(self):
        return self.with_header(rjsmin(self.content))
    def _fetch_content(self):
        try:
            return super(JavascriptAsset, self)._fetch_content()
        except AssetError, e:
            return "console.error(%s);" % json.dumps(e.message)
    def to_html(self):
        if self.url:
            return '<script type="text/javascript" src="%s"></script>' % (self.html_url)
        else:
            return '<script type="text/javascript" charset="utf-8">%s</script>' % self.with_header()
class StylesheetAsset(WebAsset):
    rx_import = re.compile(r"""@import\s+('|")(?!'|"|/|https?://)""", re.U)
    rx_url = re.compile(r"""url\s*\(\s*('|"|)(?!'|"|/|https?://|data:)""", re.U)
    rx_sourceMap = re.compile(r'(/\*# sourceMappingURL=.*)', re.U)
    rx_charset = re.compile(r'(@charset "[^"]+";)', re.U)
    def __init__(self, *args, **kw):