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
converter = self.get_converter('date')
        value = converter('2011-05-03')
        # 
        self.assertEqual(value, '05/03/2011')
    def test_datetime(self):
        converter = self.get_converter('datetime')
        value = converter('2011-05-03 11:12:13')
        # 
        self.assertEqual(value, '05/03/2011 00:12:13')
    def test_custom_format(self):
        converter = self.get_converter('datetime')
        converter2 = self.get_converter('date')
        opts = {'format': 'MMMM d'}
        value = converter('2011-03-02 11:12:13', options=opts)
        value2 = converter2('2001-03-02', options=opts)
        self.assertEqual(
            value,
            'March 2'
        )
        self.assertEqual(
            value2,
            'March 2'
        )
class TestDurationExport(TestBasicExport):