Code highlighting:

# some model to repro
class TestModel(models.Model):
    name = models.CharField(max_length=32)

# in the shell
>>> from bulk_test.models import TestModel
>>> tm=TestModel(name='hello')
>>> tm.save()
>>> tm.name
'hello'
>>> tm.name='m'*100
>>> tm.save()  # good, raises:
...
django.db.utils.DataError: value too long for type character varying(32)

>>> TestModel.objects.all().values('name')
<QuerySet [{'name': 'hello'}]>
>>> TestModel.objects.all().update(name='z'*100)  # good, raises as well:
...
django.db.utils.DataError: value too long for type character varying(32)

>>> TestModel.objects.all().values('name')
<QuerySet [{'name': 'hello'}]>
>>> TestModel.objects.bulk_update([tm], ['name'])  # not raising, instead truncating:
1
>>> TestModel.objects.all().values('name')
<QuerySet [{'name': 'mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm'}]>