DurationField stores certain values incorrectly in sqlite

[chausner]

When encoding certain timedelta values in a DurationField, saving the object to a sqlite database and then reading it again, DurationField returns None.

class Foo(models.Model):
    bar = models.DurationField()

Foo.objects.create(bar=timedelta(seconds=2.05))
Foo.objects.create(bar=timedelta(seconds=3.05))

print str(Foo.objects.all()[0].length) # 'None'
print str(Foo.objects.all()[1].length) # '3.05'

I can reproduce this bug with Django 1.8.5 and 1.9.3 using sqlite as database backend. It does not occur with MySQL, so it seems to be related to how sqlite stores bigints. It renders DurationField essentially useless with sqlite.