"""Tests that the python callable is invoked on task run."""
        @task.virtualenv()
        def f():
            pass
        with dag_maker():
            ret = f()
        ret.operator.run(start_date=DEFAULT_DATE, end_date=DEFAULT_DATE)
    def test_no_system_site_packages(self, dag_maker):
        @task.virtualenv(system_site_packages=False, python_version=PYTHON_VERSION, use_dill=True)
        def f():
            try:
                import funcsigs  
            except ImportError:
                return True
            raise Exception
        with dag_maker():
            ret = f()
        ret.operator.run(start_date=DEFAULT_DATE, end_date=DEFAULT_DATE)
    def test_system_site_packages(self, dag_maker):
        @task.virtualenv(
            system_site_packages=False,
            requirements=["funcsigs"],
            python_version=PYTHON_VERSION,
            use_dill=True,
        )
        def f():