Comment 6 for bug 452790

Once again

>>> import locale
>>> locale.getlocale()
(None, None)
>>> locale.setlocale(locale.LC_ALL, '')
'pl_PL.UTF-8'
>>> locale.localeconv()['decimal_point']
','
>>> locale.atof("100,1")
100.09999999999999

So after setting the locale it worked.