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/test_converter/tests/test_html.py
def setUp(self):
        super(TestDurationExport, self).setUp()
        # 
        self.registry('res.lang').load_lang(self.cr, self.uid, 'fr_FR')
    def test_negative(self):
        converter = self.get_converter('float', 'duration')
        with self.assertRaises(ValueError):
            converter(-4)
    def test_missing_unit(self):
        converter = self.get_converter('float', 'duration')
        with self.assertRaises(ValueError):
            converter(4)
    def test_basic(self):
        converter = self.get_converter('float', 'duration')
        result = converter(4, {'unit': 'hour'}, {'lang': 'fr_FR'})
        self.assertEqual(result, u'4 heures')
        result = converter(50, {'unit': 'second'}, {'lang': 'fr_FR'})
        self.assertEqual(result, u'50 secondes')
    def test_multiple(self):
        converter = self.get_converter('float', 'duration')
        result = converter(1.5, {'unit': 'hour'}, {'lang': 'fr_FR'})
        self.assertEqual(result, u"1 heure 30 minutes")
        result = converter(72, {'unit': 'second'}, {'lang': 'fr_FR'})
        self.assertEqual(result, u"1 minute 12 secondes")
class TestRelativeDatetime(TestBasicExport):