def set_user(self, user=None):
        if user is None and 'WEBTEST_USER' in self.extra_environ:
            del self.extra_environ['WEBTEST_USER']
        if user is not None:
            self.extra_environ = self._update_environ(self.extra_environ, user)
Update the user used by the app globaly. If user is None then user
dataset/ETHPy150Open django-webtest/django-webtest/django_webtest/__init__.py/DjangoTestApp.set_user