Add a --wait flag to cfn tool

Do not wait for create, update, or delete operations to complete
without the --wait flag.  See #136.

scripts/cfn

@@ -195,6 +195,9 @@ if __name__ == "__main__":
  help="tail event log")
  parser.add_argument("-u", "--update", help="Update an existing stack",
  dest="update")
+ parser.add_argument("-w", "--wait", action="store_true",
+ help="Wait for the operation to complete and return "
+ "an appropriate error code")
  parser.add_argument("stack", nargs='?')
  values = parser.parse_args()
 
@@ -220,14 +223,15 @@ if __name__ == "__main__":
  parameters=values.params,
  capabilities=values.capabilities)
 
- for event in events:
- print_event(event)
- if event.physical_resource_id == stack_id:
- if event.resource_status in ['UPDATE_ROLLBACK_COMPLETE',
- 'UPDATE_ROLLBACK_FAILED']:
- sys.exit(1)
- if event.resource_status == 'UPDATE_COMPLETE':
- break
+ if values.wait:
+ for event in events:
+ print_event(event)
+ if event.physical_resource_id == stack_id:
+ if event.resource_status in ['UPDATE_ROLLBACK_COMPLETE',
+ 'UPDATE_ROLLBACK_FAILED']:
+ sys.exit(1)
+ if event.resource_status == 'UPDATE_COMPLETE':
+ break
 
  if values.delete:
  stack_id = get_stack_id_if_exists(conn, values.stack)
@@ -236,14 +240,15 @@ if __name__ == "__main__":
  events.read_existing()
  conn.delete_stack(stack_id)
 
- for event in events:
- print_event(event)
- if event.physical_resource_id == stack_id:
- if event.resource_status == 'DELETE_FAILED':
- print "Delete failed"
- sys.exit(1)
- elif event.resource_status == 'DELETE_COMPLETE':
- break
+ if values.wait:
+ for event in events:
+ print_event(event)
+ if event.physical_resource_id == stack_id:
+ if event.resource_status == 'DELETE_FAILED':
+ print "Delete failed"
+ sys.exit(1)
+ elif event.resource_status == 'DELETE_COMPLETE':
+ break
  else:
  print "Couldn't delete {0}: stack doesn't exist."\
  .format(values.stack)
@@ -267,20 +272,21 @@ if __name__ == "__main__":
  stack_id = create_stack(conn, values.stack, template, None,
  values.params, values.capabilities)
 
- rollback_enabled = True
+ if values.wait:
+ rollback_enabled = True
 
- for event in StackEventIterator(conn, stack_id):
- print_event(event)
- if event.physical_resource_id == stack_id:
- if rollback_enabled:
- if event.resource_status in ['ROLLBACK_COMPLETE',
- 'ROLLBACK_FAILED']:
- sys.exit(1)
- else:
- if event.resource_status == 'CREATE_FAILED':
- sys.exit(1)
- if event.resource_status == 'CREATE_COMPLETE':
- break
+  for event in StackEventIterator(conn, stack_id):
+  print_event(event)
+  if event.physical_resource_id == stack_id:
+  if rollback_enabled:
+  if event.resource_status in ['ROLLBACK_COMPLETE',
+  'ROLLBACK_FAILED']:
+  sys.exit(1)
+  else:
+  if event.resource_status == 'CREATE_FAILED':
+  sys.exit(1)
+  if event.resource_status == 'CREATE_COMPLETE':
+  break
 
  if values.resources:
  describe_resources(conn, values.stack)