我models.py如下

from django.contrib.auth.models import User
from django.db import models
from django.utils.encoding import python_2_unicode_compatible
from django.utils.timezone import now

@python_2_unicode_compatible
class Tag(models.Model):
    name = models.CharField(max_length=50, unique=True)

    class Meta:
            verbose_name = 'tag'
            verbose_name_plural = 'tags'
            ordering = ['name']

    def __str__(self):
            return self.name
.............  and so on

当我运行时，python manage.py syncdb这是我得到的错误：

itman@itman:~/djangoApp/mysite$ python manage.py syncdb
Traceback (most recent call last): 
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/lib/python2.7/dist-packages/django/core/management/__init__.py", line 443, in execute_from_command_line
    utility.execute()
  File "/usr/lib/python2.7/dist-packages/django/core/management/__init__.py", line 382, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 196, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 231, in execute
    self.validate()
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 266, in validate
    num_errors = get_validation_errors(s, app)
  File "/usr/lib/python2.7/dist-packages/django/core/management/validation.py", line 30, in get_validation_errors
    for (app_name, error) in get_app_errors().items():
  File "/usr/lib/python2.7/dist-packages/django/db/models/loading.py", line 158, in get_app_errors
    self._populate()
  File "/usr/lib/python2.7/dist-packages/django/db/models/loading.py", line 67, in _populate
    self.load_app(app_name)
  File "/usr/lib/python2.7/dist-packages/django/db/models/loading.py", line 88, in load_app
    models = import_module('.models', app_name)
  File "/usr/lib/python2.7/dist-packages/django/utils/importlib.py", line 35, in import_module
    __import__(name)
  File "/home/itman/djangoApp/mysite/bmark/models.py", line 4, in <module>
    from django.utils.encoding import python_2_unicode_compatible
ImportError: cannot import name python_2_unicode_compatible

我不知道为什么不导入该模块。我正在使用Python 2.7和Django 1.4。