Fixed circlular import with RDS and CF

moto/rds/exceptions.py

@@ -36,3 +36,13 @@ class DBSubnetGroupNotFoundError(RDSClientError):
             "DBSubnetGroupNotFound",
             "Subnet Group {0} not found.".format(subnet_group_name),
         )
+
+
+class UnformattedGetAttTemplateException(Exception):
+    """Duplicated from CloudFormation to prevent circular deps."""
+
+    description = (
+        "Template error: resource {0} does not support attribute type {1} in Fn::GetAtt"
+    )
+
+    status_code = 400

moto/rds/models.py

@@ -3,10 +3,10 @@ from __future__ import unicode_literals
 import boto.rds
 from jinja2 import Template
 
-from moto.cloudformation.exceptions import UnformattedGetAttTemplateException
 from moto.core import BaseBackend, BaseModel
 from moto.core.utils import get_random_hex
 from moto.ec2.models import ec2_backends
+from moto.rds.exceptions import UnformattedGetAttTemplateException
 from moto.rds2.models import rds2_backends