workaround for a regression in Django 1.4 which makes forms with fields of type BooleanField non-picklable

widgets.py

"""
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"""

from django.forms.util import flatatt
from django.forms.widgets import Widget
from django.utils.encoding import force_unicode
from django.utils.safestring import mark_safe

def boolean_check(v):
    return not (v is False or v is None or v == '')


class PicklableCheckboxInput(Widget):
    def __init__(self, attrs=None, check_test=None):
        super(PicklableCheckboxInput, self).__init__(attrs)
        # check_test is a callable that takes a value and returns True
        # if the checkbox should be checked for that value.
        self.check_test = boolean_check if check_test is None else check_test

    def render(self, name, value, attrs=None):
        final_attrs = self.build_attrs(attrs, type='checkbox', name=name)
        try:
            result = self.check_test(value)
        except: # Silently catch exceptions
            result = False
        if result:
            final_attrs['checked'] = 'checked'
        if not (value is True or value is False or value is None or value == ''):
            # Only add the 'value' attribute if a value is non-empty.
            final_attrs['value'] = force_unicode(value)
        return mark_safe(u'<input%s />' % flatatt(final_attrs))

    def value_from_datadict(self, data, files, name):
        if name not in data:
            # A missing value means False because HTML form submission does not
            # send results for unselected checkboxes.
            return False
        value = data.get(name)
        # Translate true and false strings to boolean values.
        values =  {'true': True, 'false': False}
        if isinstance(value, basestring):
            value = values.get(value.lower(), value)
        return value

    def _has_changed(self, initial, data):
        # Sometimes data or initial could be None or u'' which should be the
        # same thing as False.
        return bool(initial) != bool(data)