Check RDS storage type is not io1 (#359)

* Check RDS storage type is not io1

* Rename a test file

Because we're checking not just for "io1" but also anything that starts with "io".

* Make black happy

aws/rds/test_rds_db_instance_storage_type_not_piops.py

@@ -0,0 +1,17 @@
+import pytest
+
+from aws.rds.helpers import get_db_instance_id
+from aws.rds.resources import rds_db_instances_with_tags
+
+
+@pytest.mark.rds
+@pytest.mark.parametrize(
+    "rds_db_instance", rds_db_instances_with_tags(), ids=get_db_instance_id,
+)
+def test_rds_db_instance_storage_type_not_piops(rds_db_instance):
+    """PIOPs storage type is expensive. Cloudops recommends using gp2 type with
+    a volume size that offers the same IOPs as the desired PIOPs type.
+    """
+    assert not rds_db_instance["StorageType"].startswith(
+        "io"
+    ), f"{rds_db_instance['DBInstanceIdentifier']} uses PIOPs storage type with IOPs of {rds_db_instance['Iops']}"