PythonVirtualenvOperator with provide_context=True does not have 'ti' keyword

**Apache Airflow version**: 1.10.13 **Environment**: Docker (Ubuntu 18.4 - Python 3.7) - Cloud provider or hardware configuration: Azure - OS (e.g. from /etc/os-release): Docker (Ubuntu 18.4 - Python 3.7) - Kernel (e.g. uname -a): Docker (Ubuntu 18.4 - Python 3.7) - Install tools: N/A - Others: N/A **What happened:** When we enable provide_context=True for PythonVirtualenvOperator and try to use the xcom_push to pass a variable I get this error: `File "/tmp/venv0upgqome/script.py", line 13, in push\n kwargs[\'ti\'].xcom_push(key=\'value from pusher 1\', value=value_1)\nKeyError: \'ti\'\n'` **How to reproduce it:** ``` import airflow from airflow import DAG from airflow.operators.python_operator import PythonVirtualenvOperator args = { 'owner': 'Airflow', 'start_date': airflow.utils.dates.days_ago(2), } dag = DAG('BAtatas', schedule_interval="@once", default_args=args) def push(**kwargs): """Pushes an XCom without a specific target""" value_1 = [1, 2, 3] print("printing the kwargs!!!") print(kwargs) kwargs['ti'].xcom_push(key='value from pusher 1', value=value_1) def push_by_returning(**kwargs): value_2 = {'a': 'b'} """Pushes an XCom without a specific target, just by returning it""" return value_2 def puller(**kwargs): value_2 = {'a': 'b'} value_1 = [1, 2, 3] """Pull all previously pushed XComs and check if the pushed values match the pulled values.""" ti = kwargs['ti'] # get value_1 pulled_value_1 = ti.xcom_pull(key=None, task_ids='push') assert pulled_value_1 == value_1 # get value_2 pulled_value_2 = ti.xcom_pull(task_ids='push_by_returning') assert pulled_value_2 == value_2 # get both value_1 and value_2 pulled_value_1, pulled_value_2 = ti.xcom_pull( key=None, task_ids=['push', 'push_by_returning']) assert (pulled_value_1, pulled_value_2) == (value_1, value_2) push1 = PythonVirtualenvOperator( task_id='push', dag=dag, python_callable=push, requir…