AWS tests: cleanup image deletion checking

This is a follow-on to I3279c3b5cb8cf26d390835fd0a7049bc43ec40b5

As discussed in the referenced issue, the blank return and
AttributeError here is the correct way to determine a recently deleted
image.  We don't need to catch the ClientError as that won't be raised
any more.  Getting a value for the state would indicate it wasn't
deleted.

This bumps the moto base requirement to ensure we have this behaviour.

Change-Id: I2d5b0ccb9802aa0d4c81555a17f40fe8b8595ebd

nodepool/tests/unit/test_driver_aws.py

@@ -487,20 +487,13 @@ class TestDriverAws(tests.DBTestCase):
         for _ in iterate_timeout(30, Exception, 'ami deletion'):
             image = self.ec2.Image(image_id)
             try:
-                if image.state == 'deleted':
-                    break
-            except botocore.exceptions.ClientError:
-                # Probably not found
-                break
+                # If this has a value the image was not deleted
+                self.assertIsNone(image.state)
             except AttributeError:
-                # NOTE(ianw) 2022-04-27 For reasons that are unclear
-                # but have been filed as
-                #  https://github.com/spulec/moto/issues/5067
-                # accessing the image.state property of a deleted image
-                # with moto 1.3.6  will no longer result in the ClientError
-                # above, but boto will get blank response and try to
-                # dereference a None value.  Thus catching this is a
-                # work-around until we have a better solution.
+                # Per AWS API, a recently deleted image is empty and
+                # looking at the state raises an AttributeFailure; see
+                # https://github.com/boto/boto3/issues/2531.  The image
+                # was deleted, so we continue on here
                 break
 
         for _ in iterate_timeout(30, Exception, 'snapshot deletion'):

test-requirements.txt

@@ -6,5 +6,5 @@ python-subunit
 stestr>=1.0.0 # Apache-2.0
 testscenarios
 testtools>=0.9.27
-moto
+moto>=3.1.6
 responses>=0.12.1