change: Integration Tests now dynamically checks AZs (#989)

Canaries have failed in Tokyo (ap-northeast-1) since inception because
the ap-northeast-1b region doesn't exist.

This commit makes the check dynamic instead of blindly assuming that
a and b exist, as that isn't the case for 3 regions:
ap-northeast-1
ap-northeast-2
sa-east-1

tests/integ/vpc_test_utils.py

@@ -51,13 +51,16 @@ def _create_vpc_with_name(ec2_client, region, name):
     vpc_id = ec2_client.create_vpc(CidrBlock="10.0.0.0/16")["Vpc"]["VpcId"]
     print("created vpc: {}".format(vpc_id))
 
-    # sagemaker endpoints require subnets in at least 2 different AZs for vpc mode
+    availability_zone_name = ec2_client.describe_availability_zones()["AvailabilityZones"][0][
+        "ZoneName"
+    ]
+
     subnet_id_a = ec2_client.create_subnet(
-        CidrBlock="10.0.0.0/24", VpcId=vpc_id, AvailabilityZone=(region + "a")
+        CidrBlock="10.0.0.0/24", VpcId=vpc_id, AvailabilityZone=availability_zone_name
     )["Subnet"]["SubnetId"]
     print("created subnet: {}".format(subnet_id_a))
     subnet_id_b = ec2_client.create_subnet(
-        CidrBlock="10.0.1.0/24", VpcId=vpc_id, AvailabilityZone=(region + "b")
+        CidrBlock="10.0.1.0/24", VpcId=vpc_id, AvailabilityZone=availability_zone_name
     )["Subnet"]["SubnetId"]
     print("created subnet: {}".format(subnet_id_b))