Here is is a more generic context manager built from contextlib.
from contextlib import contextmanager
@contextmanager
def temporary_changed_attr(object, attr, value):
if hasattr(object, attr):
old = getattr(object, attr)
setattr(object, attr, value)
yield
setattr(object, attr, old)
else:
setattr(object, attr, value)
yield
delattr(object, attr)
# Example usage
with temporary_changed_attr(self.testuser, 'is_active', False):
# self.testuser.is_active will be false in here