runserver causes "No module named 'django.core.urlresolvers'" to be raised

Environment Snapshot for Reproduction

Django==2.0.2
djangorestframework==3.7.7
drf-extensions==0.3.1

Problem

Running python manage.py runserver causes the following error to be thrown:

Unhandled exception in thread started by <function check_errors.<locals>.wrapper at 0x7f9a60df2ea0>
Traceback (most recent call last):
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/django/utils/autoreload.py", line 225, in wrapper
    fn(*args, **kwargs)
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/django/core/management/commands/runserver.py", line 121, in inner_run
    self.check(display_num_errors=True)
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/django/core/management/base.py", line 364, in check
    include_deployment_checks=include_deployment_checks,
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/django/core/management/base.py", line 351, in _run_checks
    return checks.run_checks(**kwargs)
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/django/core/checks/registry.py", line 73, in run_checks
    new_errors = check(app_configs=app_configs)
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/django/core/checks/urls.py", line 40, in check_url_namespaces_unique
    all_namespaces = _load_all_namespaces(resolver)
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/django/core/checks/urls.py", line 57, in _load_all_namespaces
    url_patterns = getattr(resolver, 'url_patterns', [])
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/django/utils/functional.py", line 36, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/django/urls/resolvers.py", line 536, in url_patterns
    patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/django/utils/functional.py", line 36, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/django/urls/resolvers.py", line 529, in urlconf_module
    return import_module(self.urlconf_name)
  File "/home/ldavid/envs/tf/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 994, in _gcd_import
  File "<frozen importlib._bootstrap>", line 971, in _find_and_load
  File "<frozen importlib._bootstrap>", line 955, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 665, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/ldavid/repos/recod/mlswarm-api/mlswarm_api/urls.py", line 4, in <module>
    from rest_framework_extensions.routers import ExtendedDefaultRouter
  File "/home/ldavid/envs/tf/lib/python3.6/site-packages/rest_framework_extensions/routers.py", line 4, in <module>
    from django.core.urlresolvers import NoReverseMatch
ModuleNotFoundError: No module named 'django.core.urlresolvers'

Work-around

I managed to work around this by navigating to rest_framework_extensions/routes.py and replacing

from django.core.urlresolvers import NoReverseMatch

with

from django.urls import NoReverseMatch

[chancegraff]

I believe that this is still a problem. The code from master located at https://github.com/chibisov/drf-extensions/blob/master/rest_framework_extensions/routers.py still shows as:

try:
    from django.urls.resolvers import NoReverseMatch
except ImportError:
    from django.core.urlresolvers import NoReverseMatch

It should be changed to:

from django.urls import NoReverseMatch

There’s a test here that imports it correctly:

https://github.com/chibisov/drf-extensions/blob/master/tests_app/tests/functional/routers/extended_default_router/tests.py

[auvipy]

hope before the end of the month, actually have to contribute to multiple project so time is so scarce