id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
32100	Parameter KEY_PREFIX for DummyCache causing test runner to fail	Kaustubh Bhalerao	nobody	"Summary: 
If the KEY_PREFIX option is present while using the DummyCache backend, the test runner fails with the traceback at the bottom. When running the server, there via runserver there is no issue. 

{{{
CACHES = {
    'default': {
        'BACKEND': 'django.core.cache.backends.dummy.DummyCache',
    },
    'KEY_PREFIX': ""SomeKeyPrefix""
}
}}}

{{{
Traceback (most recent call last):
  File ""/snap/pycharm-professional/215/plugins/python/helpers/pycharm/django_test_manage.py"", line 168, in <module>
    utility.execute()
  File ""/snap/pycharm-professional/215/plugins/python/helpers/pycharm/django_test_manage.py"", line 142, in execute
    _create_command().run_from_argv(self.argv)
  File ""/home/.../lib/python3.8/site-packages/django/core/management/commands/test.py"", line 23, in run_from_argv
    super().run_from_argv(argv)
  File ""/home/.../DJ3/lib/python3.8/site-packages/django/core/management/base.py"", line 328, in run_from_argv
    self.execute(*args, **cmd_options)
  File ""/home/.../lib/python3.8/site-packages/django/core/management/base.py"", line 369, in execute
    output = self.handle(*args, **options)
  File ""/snap/pycharm-professional/215/plugins/python/helpers/pycharm/django_test_manage.py"", line 104, in handle
    failures = TestRunner(test_labels, **options)
  File ""/snap/pycharm-professional/215/plugins/python/helpers/pycharm/django_test_runner.py"", line 254, in run_tests
    return DjangoTeamcityTestRunner(**options).run_tests(test_labels,
  File ""/snap/pycharm-professional/215/plugins/python/helpers/pycharm/django_test_runner.py"", line 156, in run_tests
    return super(DjangoTeamcityTestRunner, self).run_tests(test_labels, extra_tests, **kwargs)
  File ""/home/.../lib/python3.8/site-packages/django/test/runner.py"", line 684, in run_tests
    old_config = self.setup_databases(aliases=databases)
  File ""/home/.../lib/python3.8/site-packages/django/test/runner.py"", line 604, in setup_databases
    return _setup_databases(
  File ""/home/.../lib/python3.8/site-packages/django/test/utils.py"", line 169, in setup_databases
    connection.creation.create_test_db(
  File ""/home/.../lib/python3.8/site-packages/django/db/backends/base/creation.py"", line 82, in create_test_db
    call_command('createcachetable', database=self.connection.alias)
  File ""/home/.../lib/python3.8/site-packages/django/core/management/__init__.py"", line 168, in call_command
    return command.execute(*args, **defaults)
  File ""/home/.../lib/python3.8/site-packages/django/core/management/base.py"", line 369, in execute
    output = self.handle(*args, **options)
  File ""/home/.../lib/python3.8/site-packages/django/core/management/commands/createcachetable.py"", line 42, in handle
    cache = caches[cache_alias]
  File ""/home/.../lib/python3.8/site-packages/django/core/cache/__init__.py"", line 79, in __getitem__
    cache = _create_cache(alias)
  File ""/home/.../lib/python3.8/site-packages/django/core/cache/__init__.py"", line 47, in _create_cache
    params = {**conf, **kwargs}
TypeError: 'str' object is not a mapping
}}}

Error message is pretty clear, but likely requires a more general solution implemented in createcachetable.py when DummyCache backend is being used. 

Workaround: Do not add options to DummyCache backend, and potentially update documentation to indicate if options to DummyCache will be a problem. "	Bug	closed	Core (Cache system)	3.1	Normal	invalid			Unreviewed	0	0	0	0	0	0