import json

from django.db import models

try:
    unicode
except NameError:
    unicode = str


class DjangoJSONEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, models.Model) and hasattr(obj, 'as_data'):
            return obj.as_data()
        return json.JSONEncoder.default(self, obj)


def get_data(error):
    if isinstance(error, (dict, str)):
        return error
    return error.get_json_data()


class JSONMixin(object):
    def as_json(self):
        return json.dumps(self.as_data(), cls=DjangoJSONEncoder)

    def as_data(self):
        return {
            'fields': {
                str(name): self.field_to_dict(name, field) for name, field in self.fields.items()
            },
            'errors': {f: get_data(e) for f, e in self.errors.items()},
            'nonFieldErrors': [get_data(e) for e in self.non_field_errors()]
        }

    def field_to_dict(self, name, field):
        return {
            "type": field.__class__.__name__,
            "widget_type": field.widget.__class__.__name__,
            "hidden": field.widget.is_hidden,
            "required": field.widget.is_required,
            "label": str(field.label),
            "help_text": str(field.help_text),
            "initial": self.get_initial_for_field(field, name),
            "placeholder": str(field.widget.attrs.get('placeholder', '')),
            "value": self[name].value() if self.is_bound else None
        }

import json

from django.db import models

try:
    str = unicode
except NameError:
    pass


class DjangoJSONEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, models.Model) and hasattr(obj, 'as_data'):
            return obj.as_data()
        return json.JSONEncoder.default(self, obj)


def get_data(error):
    if isinstance(error, (dict, str)):
        return error
    return error.get_json_data()


class JSONMixin(object):
    def as_json(self):
        return json.dumps(self.as_data(), cls=DjangoJSONEncoder)

    def as_data(self):
        return {
            'fields': {
                str(name): self.field_to_dict(name, field) for name, field in self.fields.items()
            },
            'errors': {f: get_data(e) for f, e in self.errors.items()},
            'nonFieldErrors': [get_data(e) for e in self.non_field_errors()]
        }

    def field_to_dict(self, name, field):
        return {
            "type": field.__class__.__name__,
            "widget_type": field.widget.__class__.__name__,
            "hidden": field.widget.is_hidden,
            "required": field.widget.is_required,
            "label": str(field.label),
            "help_text": str(field.help_text),
            "initial": self.get_initial_for_field(field, name),
            "placeholder": str(field.widget.attrs.get('placeholder', '')),
            "value": self[name].value() if self.is_bound else None
        }

Redefine str to be unicode on Python 2.7 in module