The new version of botcore adds this region: f7dc4730ad (diff-9dfab05d4ba739e097a193e8b5fa61caR13)
Which in turn, breaks moto:
```
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/__init__.py:3: in <module>
from .acm import mock_acm # noqa
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/acm/__init__.py:2: in <module>
from .models import acm_backends
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/acm/models.py:7: in <module>
from moto.ec2 import ec2_backends
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/__init__.py:2: in <module>
from .models import ec2_backends
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:5169: in <module>
ec2_backends = {
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:5170: in <dictcomp>
region.name: EC2Backend(region.name) for region in RegionsAndZonesBackend.regions
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:5083: in __init__
super(EC2Backend, self).__init__()
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:852: in __init__
super(InstanceBackend, self).__init__()
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:1127: in __init__
super(TagBackend, self).__init__()
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:2368: in __init__
super(EBSBackend, self).__init__()
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:1904: in __init__
super(SecurityGroupBackend, self).__init__()
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:1355: in __init__
self._load_amis()
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:1362: in _load_amis
self.amis[ami_id] = Ami(self, **ami)
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:1313: in __init__
volume = self.ec2_backend.create_volume(15, region_name)
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:2372: in create_volume
zone = self.get_zone_by_name(zone_name)
/moto-1.3.15.dev640-py2.py3-none-any.whl/moto/ec2/models.py:1713: in get_zone_by_name
for zone in self.zones[self.region_name]:
E KeyError: 'af-south-1'
```
When loading AMIS and INSTANCE_TYPES in moto.ec2.models a file handle is
potentially leaked when loading the JSON. This results in a
ResourceWarning which is a bit of unnecessary noise.
Rather than pass a call to open() to json.load() this instead uses a
context-manager in a small private helper function.
This fixes https://github.com/spulec/moto/issues/2620
