boto (2) modules have no support for new regions

Description of Issue

Trying to use salt-call boto_cfn.exists mystack region=eu-north-1
and getting response
Passed invalid arguments: Region "eu-north-1" is not valid..

$ python3
>>> import boto
>>> from boto import cloudformation
>>> cloudformation.regions()
[RegionInfo:eu-west-2, RegionInfo:eu-central-1, RegionInfo:us-east-2, RegionInfo:ap-southeast-2, RegionInfo:ap-northeast-2, RegionInfo:ap-northeast-1, RegionInfo:cn-north-1, RegionInfo:ap-south-1, RegionInfo:us-west-1, RegionInfo:us-east-1, RegionInfo:us-gov-west-1, RegionInfo:us-west-2, RegionInfo:ap-southeast-1, RegionInfo:ca-central-1, RegionInfo:sa-east-1, RegionInfo:eu-west-1]

It seems like boto2, and subsequently all (?) modules depending on this dont have support for any new AWS regions.

Setup

(Please provide relevant configs and/or SLS files (Be sure to remove sensitive info).)

Steps to Reproduce Issue

(Include debug logs if possible and relevant.)

Versions Report

pip3 list
boto (2.49.0)
boto3 (1.12.13)
botocore (1.15.13)

> salt-call -V
Salt Version:
           Salt: 2019.2.3

Dependency Versions:
           cffi: 1.14.0
       cherrypy: 5.6.0
       dateutil: 2.8.1
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
          ioflo: Not Installed
         Jinja2: 2.8.1
        libgit2: 0.28.2
        libnacl: Not Installed
       M2Crypto: 0.35.2
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.5.6
   mysql-python: Not Installed
      pycparser: 2.19
       pycrypto: Not Installed
   pycryptodome: Not Installed
         pygit2: 0.28.2
         Python: 3.6.8 (default, Apr 25 2019, 21:02:35)
   python-gnupg: Not Installed
         PyYAML: 5.3
          PyZMQ: 15.3.0
           RAET: Not Installed
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.4.2
            ZMQ: 4.1.4

System Versions:
           dist: centos 7.6.1810 Core
         locale: UTF-8
        machine: x86_64
        release: 3.10.0-957.21.3.el7.x86_64
         system: Linux
        version: CentOS Linux 7.6.1810 Core

Start with the reported salt-call boto_cfn.exists mystack region=eu-north-1 entry point and inspect how the boto2 modules obtain and validate AWS regions. Reproduce the invalid-region response, then confirm that eu-north-1 and other new regions are accepted by the affected modules.