エラー: The policy failed legacy parsing

Serverlessを使っていて以下のエラー。

エラー

  Serverless Error ---------------------------------------

  An error occurred: MicroServiceAdminGroupPolicy - The policy failed legacy parsing (Service: AmazonIdentityManagement; Status Code: 400; Error Code: MalformedPolicyDocument; Request ID: xxx-xxx).

  Get Support --------------------------------------------
     Docs:          docs.serverless.com
     Bugs:          github.com/serverless/serverless/issues
     Issues:        forum.serverless.com

  Your Environment Information ---------------------------
     Operating System:          darwin
     Node Version:              12.4.0
     Framework Version:         1.63.0
     Plugin Version:            3.3.0
     SDK Version:               2.3.0
     Components Core Version:   1.1.2
     Components CLI Version:    1.4.0

テンプレートの内容

  MicroServiceAdminGroupPolicy:
    Type: AWS::IAM::ManagedPolicy
    Properties:
      Description: "foobar"
      Groups:
        - !Ref MicroServiceAdminGroup
      PolicyDocument:
        Version: '2012-10-17'
        Statement:
          # DynamoDB
          - Effect: Allow
            Action:
              - dynamodb:*
            Resource:
              - "arn:aws:dynamodb:#{AWS::Region}:#{AWS::AccountId}:table/${self:service}-*"

原因

↓こいつらが原因。

• #{AWS::Region}

Serverless Pseudo Parametersの記法だが、プラグインを入れ忘れていた。プラグインを入れることで解決。

npm install serverless-pseudo-parameters --save-dev

serverless.yml

plugins:
  - serverless-pseudo-parameters