Throw exception if an update is attempted on a stack in ROLLBACK_COMPLETE

If a stack has a status of ROLLBACK_COMPLETE and you attempt to update
it, the AWS API throws a validation error. This updates moto to have the
same behvaior. We also uncommented a test which tests updating a stack
which passed without any additional modification -- it is unclear why
this test was commented.

Signed-off-by: Jack Lund <jack.lund@getbraintree.com>

moto/cloudformation/exceptions.py

@@ -9,12 +9,15 @@ class UnformattedGetAttTemplateException(Exception):
 
 
 class ValidationError(BadRequest):
-    def __init__(self, name_or_id):
+    def __init__(self, name_or_id, message=None):
+        if message is None:
+            messgae="Stack:{0} does not exist".format(name_or_id),
+
         template = Template(ERROR_RESPONSE)
         super(ValidationError, self).__init__()
         self.description = template.render(
             code="ValidationError",
-            message="Stack:{0} does not exist".format(name_or_id),
+            message=message,
         )
 
 

moto/cloudformation/responses.py

@@ -129,6 +129,10 @@ class CloudFormationResponse(BaseResponse):
         else:
             stack_body = self._get_param('TemplateBody')
 
+        stack = self.cloudformation_backend.get_stack(stack_name)
+        if stack.status == 'ROLLBACK_COMPLETE':
+            raise ValidationError(stack.stack_id, message="Stack:{0} is in ROLLBACK_COMPLETE state and can not be updated.".format(stack.stack_id))
+
         stack = self.cloudformation_backend.update_stack(
             name=stack_name,
             template=stack_body,

tests/test_cloudformation/test_cloudformation_stack_crud.py

@@ -13,6 +13,7 @@ import tests.backport_assert_raises  # noqa
 from nose.tools import assert_raises
 
 from moto import mock_cloudformation, mock_s3
+from moto.cloudformation import cloudformation_backends
 
 dummy_template = {
     "AWSTemplateFormatVersion": "2010-09-09",
@@ -286,6 +287,7 @@ def test_update_stack():
         }
     })
 
+
 @mock_cloudformation
 def test_update_stack():
     conn = boto.connect_cloudformation()
@@ -307,3 +309,20 @@ def test_update_stack():
             }
         }
     })
+
+
+@mock_cloudformation
+def test_update_stack_when_rolled_back():
+    conn = boto.connect_cloudformation()
+    stack_id = conn.create_stack("test_stack", template_body=dummy_template_json)
+
+    cloudformation_backends[conn.region.name].stacks[stack_id].status = 'ROLLBACK_COMPLETE'
+
+    with assert_raises(BotoServerError) as err:
+        conn.update_stack("test_stack", dummy_template_json)
+
+    ex = err.exception
+    ex.body.should.match(r'is in ROLLBACK_COMPLETE state and can not be updated')
+    ex.error_code.should.equal('ValidationError')
+    ex.reason.should.equal('Bad Request')
+    ex.status.should.equal(400)