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Changes between Version 1 and Version 2 of Ticket #21977, comment 14

v1	v2
1		While this fix will clear the cache ''when the ROOT_URLCONF is overridden'', it does nothing to clear them ''once that override goes out of scope''. As a result once you override ROOT_URLCONF, that override leaks out to all subsequent unit tests if they don't explicitly override it too.
	1	https://github.com/django/django/blob/master/django/core/handlers/base.py#L122
2	2
3		~~Actually on a second look it seems it might intend to do that too, but I ''am'' seeing leaking overrides in my tests, will investigate it more~~.
	3	Performing any request while @override.settings(ROOT_URLCONF) is in effect stores that override in the [https://github.com/django/django/blob/master/django/urls/base.py#L21 django.urls.base._urlconfs] thread local and nothing takes care to clean it up afterwards. This leads to leaking — once ROOT_URLCONF is overridden, it remains in effect even after the override goes out of scope and applies to all subsequent tests that try to resolve URLs before they perform a request (which is what would usually happen).