Make sure you have checked _all_ steps below. ### Jira
- [X] My PR addresses the following [Airflow Jira](https://issues.apache.org/jira/browse/AIRFLOW/) issues and references them in the PR title. For example, "\[AIRFLOW-XXX\] My Airflow PR" - https://issues.apache.org/jira/browse/AIRFLOW-2936 ### Description - [X] Make Docker image use official Python images for base images. ### Commits - [X] My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "[How to write a good git commit message](http://chris.beams.io/posts/git-commit/)": [ Full content available at: https://github.com/apache/incubator-airflow/pull/3782 ] This message was relayed via gitbox.apache.org for [email protected]
