title: Serverless create snspolicy fails with invalid parameter
body: <p>Here is the error.</p>
  
  <pre><code>An error occurred: SNSTopicPolicy - Invalid parameter:
  Policy Error: null (Service: AmazonSNS; 
  Status Code: 400; Error Code: InvalidParameter; 
  Request ID: 38a567df-2cff-50bf-8f0e-33a91775cc6e).
  </code></pre>
  
  <p>I cannot find a place to look into logs to tell me what parameter is missing.?.?  I'm pretty sure I have everything that is required.  I'm using this <a href="https://docs.aws.amazon.com/sns/latest/dg/sns-sqs-as-subscriber.html" rel="nofollow noreferrer">site</a> and their api pages.</p>
  
  <pre><code>SNSTopic:
    Type: AWS::SNS::Topic
    Properties:
      DisplayName: Aura main Topic
      TopicName: ${file(./env.yml):${opt:stage, self:provider.stage}.env.auraSnsTopicName}
  
  SNSTopicPolicy:
    Type: AWS::SNS::TopicPolicy
    Properties:
      PolicyDocument:
        Id: auraAllowSQSsendrobelrobel
        Statement:
          -
            Effect: Allow
            Action:
              - sns: Publish
            Resource: { "Fn::GetAtt":["SQSQueue" ,"Arn"]}
            Principle:
              AWS: "*"
      Topics:
        - { "Ref": "SNSTopic" }
  
  
  SQSQueue:
    Type: AWS::SQS::Queue
    Properties:
      QueueName: ${file(./env.yml):${opt:stage, self:provider.stage}.env.eeegPagesQueueName}
      RedrivePolicy:
        deadLetterTargetArn: {"Fn::GetAtt" : [ "SQSQueueDLQ", "Arn" ]}
        maxReceiveCount: 2
  
  
  SQSQueuePolicy:
    Type: AWS::SQS::QueuePolicy
    Properties:
      PolicyDocument:
        Id: allowSNSSourceAndLambdaTrigger
        Statement:
          -
            Effect: Allow
            Action:
              - SQS:ReceiveMessage
              - SQS:SendMessage
              - SQS:ChangeMessageVisibility
              - SQS:ListDeadLetterSourceQueues
              - SQS:GetQueueUrl
              # - lambda:CreateEventSourceMapping
              # - lambda:ListEventSourceMappings
              # - lambda:ListFunction
            Resource: {"Ref": "SNSTopic"}
      Queues:
        - { "Ref": "SQSQueue" }
  </code></pre>
  
  <p>I have an SQS Policy statement that is working just fine.</p>
  
  <pre><code>  Your Environment Information ----------------------------
       OS:                    Mac darwin
       Node Version:           8.12.0
       Serverless Version:     1.32.0
  </code></pre>