Advanced deprecation warnings for Django 3.1.

tests/runtests.py

@@ -24,9 +24,7 @@ else:
     from django.test.runner import default_test_processes
     from django.test.selenium import SeleniumTestCaseBase
     from django.test.utils import get_runner
-    from django.utils.deprecation import (
-        RemovedInDjango31Warning, RemovedInDjango40Warning,
-    )
+    from django.utils.deprecation import RemovedInDjango40Warning
     from django.utils.log import DEFAULT_LOGGING
     from django.utils.version import PY37
 
@@ -40,7 +38,6 @@ else:
 
 # Make deprecation warnings errors to ensure no usage of deprecated features.
 warnings.simplefilter("error", RemovedInDjango40Warning)
-warnings.simplefilter('error', RemovedInDjango31Warning)
 # Make runtime warning errors to ensure no usage of error prone patterns.
 warnings.simplefilter("error", RuntimeWarning)
 # Ignore known warnings in test dependencies.