Handle reverse_lazy

Fixes #209.

src/drf_yasg/renderers.py

@@ -1,6 +1,7 @@
 import six
 
 from django.shortcuts import render, resolve_url
+from django.utils.functional import Promise
 from rest_framework.renderers import BaseRenderer, JSONRenderer, TemplateHTMLRenderer
 from rest_framework.utils import json
 
@@ -81,6 +82,9 @@ class _UIRenderer(BaseRenderer):
         renderer_context.update(self.get_auth_urls())
 
     def resolve_url(self, to):
+        if isinstance(to, Promise):
+            to = str(to)
+
         if to is None:
             return None
 

testproj/testproj/settings/base.py

@@ -1,6 +1,8 @@
 import os
 
 # Build paths inside the project like this: os.path.join(BASE_DIR, ...)
+from django.urls import reverse_lazy
+
 BASE_DIR = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 ALLOWED_HOSTS = [
@@ -91,7 +93,7 @@ REST_FRAMEWORK = {
 # drf-yasg
 
 SWAGGER_SETTINGS = {
-    'LOGIN_URL': '/admin/login',
+    'LOGIN_URL': reverse_lazy('admin:login'),
     'LOGOUT_URL': '/admin/logout',
 
     'DEFAULT_INFO': 'testproj.urls.swagger_info',