BooleanField no longer accepts empty string as False value

[elpescado]

As of 1.10, BooleanField no longer accepts empty string("" ) as False value. Was this change intentional? It was not mentioned in [Backwards incompatible changes in 1.10](​https://docs.djangoproject.com/en/1.10/releases/1.10/#backwards-incompatible-1-10) section of manual.

models.py:

class BooleanModel(models.Model):
    value = models.BooleanField(default=False)

tests.py:

class BooleanFieldTest(TestCase):
    def test_empty_string_as_value(self):
        BooleanModel(value="").save()

Running with Django 1.9:

 $ python manage.py test
Creating test database for alias 'default'...
.
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Ran 1 test in 0.001s

OK
Destroying test database for alias 'default'...

Running with Django 1.10:

 $ python manage.py test
Creating test database for alias 'default'...
E
======================================================================
ERROR: test_empty_string_as_value (boolapp.tests.BooleanFieldTest)
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Traceback (most recent call last):
  File "/home/sitek/tmp/boolfield/boolapp/tests.py", line 7, in test_empty_string_as_value
    BooleanModel(value="").save()
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/base.py", line 796, in save
    force_update=force_update, update_fields=update_fields)
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/base.py", line 824, in save_base
    updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/base.py", line 908, in _save_table
    result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/base.py", line 947, in _do_insert
    using=using, raw=raw)
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/query.py", line 1045, in _insert
    return query.get_compiler(using=using).execute_sql(return_id)
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 1053, in execute_sql
    for sql, params in self.as_sql():
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 1006, in as_sql
    for obj in self.query.objs
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 945, in prepare_value
    value = field.get_db_prep_save(value, connection=self.connection)
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 755, in get_db_prep_save
    prepared=False)
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 747, in get_db_prep_value
    value = self.get_prep_value(value)
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 1025, in get_prep_value
    return self.to_python(value)
  File "/home/sitek/.virtualenvs/teb110_sitek/local/lib/python2.7/site-packages/django/db/models/fields/__init__.py", line 1018, in to_python
    params={'value': value},
ValidationError: [u"'' value must be either True or False."]

----------------------------------------------------------------------
Ran 1 test in 0.004s

FAILED (errors=1)
Destroying test database for alias 'default'...