Django 2.0教程 - 执行python3 manage.py makemigrations时出错

Question

我有兴趣学习Django for python。因此，我按照他们的教程 - 但现在我被困在第二个教程元素的以下点：

问题：根据教程，我将使用以下代码运行“数据库迁移”：

python3 manage.py makemigrations
python3 manage.py migratecode

我在执行第一个命令（makemigrations）时收到以下错误消息：

> (django_second_test) sebastian@sebastian-Lenovo-Y50-70
> ~/Dokumente/py_virtualenv/django_virtualenv/django_second_test/locallibrary/locallibrary
> $ python3 manage.py makemigrations Traceback (most recent call last): 
> File "manage.py", line 15, in <module>
>     execute_from_command_line(sys.argv)   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/core/management/__init__.py", line 371, in execute_from_command_line
>     utility.execute()   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/core/management/__init__.py", line 365, in execute
>     self.fetch_command(subcommand).run_from_argv(self.argv)   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/core/management/base.py",
> line 288, in run_from_argv
>     self.execute(*args, **cmd_options)   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/core/management/base.py",
> line 332, in execute
>     self.check()   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/core/management/base.py",
> line 364, in check
>     include_deployment_checks=include_deployment_checks,   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/core/management/base.py",
> line 351, in _run_checks
>     return checks.run_checks(**kwargs)   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/core/checks/registry.py",
> line 73, in run_checks
>     new_errors = check(app_configs=app_configs)   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/core/checks/urls.py",
> line 40, in check_url_namespaces_unique
>     all_namespaces = _load_all_namespaces(resolver)   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/core/checks/urls.py",
> line 57, in _load_all_namespaces
>     url_patterns = getattr(resolver, 'url_patterns', [])   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/utils/functional.py",
> line 36, in __get__
>     res = instance.__dict__[self.name] = self.func(instance)   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/urls/resolvers.py",
> line 536, in url_patterns
>     patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)   File
> "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/utils/functional.py",
> line 36, in __get__
>     res = instance.__dict__[self.name] = self.func(instance)   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/lib/python3.5/site-packages/django/urls/resolvers.py",
> line 529, in urlconf_module
>     return import_module(self.urlconf_name)   File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
>     return _bootstrap._gcd_import(name[level:], package, level)   File "<frozen importlib._bootstrap>", line 986, in _gcd_import   File
> "<frozen importlib._bootstrap>", line 969, in _find_and_load   File
> "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked 
> File "<frozen importlib._bootstrap>", line 673, in _load_unlocked  
> File "<frozen importlib._bootstrap_external>", line 665, in
> exec_module   File "<frozen importlib._bootstrap>", line 222, in
> _call_with_frames_removed   File "/home/sebastian/Dokumente/py_virtualenv/django_virtualenv/django_second_test/locallibrary/locallibrary/locallibrary/urls.py",
> line 20, in <module>
>     url(r'^admin/', admin.site.urls),  NameError: name 'url' is not defined

我已经重新检查了我的代码，甚至根据教程规范copy_pasted - 但作为一个初学者（也在Python中）我很难理解发生了什么。

链接到教程页面：Link to second part of Django Tutorial

其他信息：虚拟环境处于活动状态（通过“source activate”激活）; Python3.5在虚拟环境中。 tutoriual的第一部分（虚拟环境和python的设置以及通过pip3安装django是成功的）。我在薄荷linux上。

感谢大家的帮助！

塞巴斯蒂安