Can't use ec2.py to pull AWS inventory from US East (GovCloud)

I noticed when trying to add an Amazon EC2 inventory source, US East (GovCloud) does not appear as an option (as I believe it is using legacy boto on the backend).

Can you provide someone who can give me a quick summary of how to upgrade ec2.py to use boto3 or somehow force it to call to us-gov-east-1?

I am running Ansible Tower 3.6.2 on CentOS.

<img src="/sites/profiles/files/discussion/images/2020-02/at.jpg" width="1161" height="515" alt="inventory settings screen" title="inventory settings screen" />