Check Refs in troposphere template

validated_template.py

import warnings

from troposphere import Template as BaseTemplate, BaseAWSObject, Ref, AWSHelperFn

from troposphere import (
    AWS_ACCOUNT_ID,
    AWS_NOTIFICATION_ARNS,
    AWS_NO_VALUE,
    AWS_REGION,
    AWS_STACK_ID,
    AWS_STACK_NAME,
)

AWS_PSEUDO_PARAMS = (
    AWS_ACCOUNT_ID,
    AWS_NOTIFICATION_ARNS,
    AWS_NO_VALUE,
    AWS_REGION,
    AWS_STACK_ID,
    AWS_STACK_NAME,
)

class Template(BaseTemplate):
    def validate_refs(self, obj=None):
       if obj is None:
           self.validate_refs(self.resources)
           self.validate_refs(self.conditions)
       elif isinstance(obj, BaseAWSObject):
           self.validate_refs(obj.properties)
       elif isinstance(obj, dict):
           for name, val in obj.iteritems():
               self.validate_refs(val)
       elif isinstance(obj, list):
           for item in obj:
               self.validate_refs(item)
       elif isinstance(obj, Ref):
           groups = [self.resources, self.conditions, self.parameters, AWS_PSEUDO_PARAMS]
           if not any([obj.data.get('Ref') in g for g in groups]):
               raise ValueError('Invalid reference: %s' % ref_name)
       elif isinstance(obj, AWSHelperFn):
           self.validate_refs(obj.data)
       elif isinstance(obj, basestring):
           pass
       else:
           warnings.warn('Ref Validation::Unknown type %s' % type(obj))