import six

def python_2_unicode_compatible(klass):

"""

A decorator that defines __unicode__ and __str__ methods under Python 2.

Under Python 3 it does nothing.

To support Python 2 and 3 with a single code base, define a __str__ method

returning text and apply this decorator to the class.

"""

if six.PY2:

if '__str__' not in klass.__dict__:

raise ValueError("@python_2_unicode_compatible cannot be applied "

"to %s because it doesn't define __str__()." %

klass.__name__)

klass.__unicode__ = klass.__str__

klass.__str__ = lambda self: self.__unicode__().encode('utf-8')

return klass