add Django 4.0 (currently in Alpha 1) to test matrix

.ci/.jenkins_exclude.yml

@@ -1,6 +1,14 @@
 exclude:
   - PYTHON_VERSION: pypy-3  # pypy3 currently fails on CI, e.g. https://apm-ci.elastic.co/blue/organizations/jenkins/apm-agent-python%2Fapm-agent-python-mbp/detail/PR-1099/2/pipeline#step-3497-log-1
     FRAMEWORK: none
+  # Django
+    # Django 4.0 requires Python 3.8+
+  - PYTHON_VERSION: pypy-3 # current pypy-3 is compatible with Python 3.7
+    FRAMEWORK: django-4.0
+  - PYTHON_VERSION: python-3.6
+    FRAMEWORK: django-4.0
+  - PYTHON_VERSION: python-3.7
+    FRAMEWORK: django-4.0
   # Flask
   - PYTHON_VERSION: pypy-3
     FRAMEWORK: flask-0.11 # see https://github.com/pallets/flask/commit/6e46d0cd, 0.11.2 was never released

.ci/.jenkins_framework.yml

@@ -6,6 +6,7 @@ FRAMEWORK:
   - django-2.0
   - django-3.1
   - django-3.2
+  - django-4.0
   - flask-0.12
   - flask-1.1
   - flask-2.0

.ci/.jenkins_framework_full.yml

@@ -9,6 +9,7 @@ FRAMEWORK:
   - django-3.0
   - django-3.1
   - django-3.2
+  - django-4.0
     #  - django-master
   - flask-0.10
   - flask-0.11

tests/contrib/django/testapp/urls.py

@@ -37,7 +37,7 @@
 from tests.contrib.django.testapp import views
 
 try:
-    from django.conf.urls import re_path
+    from django.urls import re_path
 except ImportError:
     # Django < 2
     from django.conf.urls import url as re_path

tests/requirements/reqs-django-4.0.txt

@@ -0,0 +1,2 @@
+Django>=4.0a1,<4.1
+-r reqs-base.txt