title: Specify ImageUri in AWS::Lambda::Function throws CF error
body: <p>For some reason I'm unable to figure out why this is going wrong.</p>
  <p>I've created a public ECR repository and I try to refer the image as <code>ImageUri</code> under the <code>Code</code> block in my AWS::Lambda::Function.</p>
  <pre><code>  SlackNotifierFunction:
      Type: AWS::Lambda::Function
      Properties:
        FunctionName: !Join [&quot;-&quot;, [!Ref Name, &quot;slack&quot;, &quot;notifier&quot;]]
        Role: !GetAtt LambdaRole.Arn
        Code:
          ImageUri: public.ecr.aws/g9c9m7n7/aws-cost-anomaly-slack-notifier:latest
        Timeout: 1
        MemorySize: 128
        PackageType: Image
        Architectures: [&quot;arm64&quot;]
        Environment:
          Variables:
            LOG_LEVEL: INFO
            SLACK_TOKEN: !Ref SlackToken
            SLACK_CHANNEL: !Ref SlackChannel
  </code></pre>
  <p>CloudFormation throws the following error whilst creating the Lambda function.</p>
  <blockquote>
  <p>Resource handler returned message: &quot;Source image
  public.ecr.aws/g9c9m7n7/aws-cost-anomaly-slack-notifier:latest
  is not valid. Provide a valid source image. (Service: Lambda, Status
  Code: 400, Request ID: 9150921d-4b35-44ae-a4eb-c137f2a779e9, Extended
  Request ID: null)&quot; (RequestToken:
  616bb226-a46b-faf1-c959-aad09880b137, HandlerErrorCode:
  InvalidRequest)</p>
  </blockquote>
  <p>Here's the ECR public gallery link: <a href="https://gallery.ecr.aws/g9c9m7n7/aws-cost-anomaly-slack-notifier" rel="nofollow noreferrer">https://gallery.ecr.aws/g9c9m7n7/aws-cost-anomaly-slack-notifier</a></p>