title: Getting 'Property IpProtocol cannot be empty' error while creating security group using cloud formation
body: <p>I am creating a basic security group using cloud formation on AWS but I am getting <em>Property IpProtocol cannot be empty.</em> error. Following is the yml code I am running:</p>
  
  <pre><code>Resources:
      testsecuritygroup:
      Type: AWS::EC2::SecurityGroup
      Properties: 
        GroupName: test-group
        GroupDescription: test security group
        SecurityGroupIngress:
          - IpProtocol: tcp
            FromPort: 80
            ToPort: 80
          - SourceSecurityGroupId: sg-xxxxxxxxxx
        SecurityGroupEgress:
          - IpProtocol: tcp
            FromPort: 80
            ToPort: 80
            CidrIp: 0.0.0.0
        Tags:
          - Key: group
            Value: test
        VpcId: !ImportValue VPC
  </code></pre>
  
  <p>When I run create-stack command it is running successfully but the stack is rolled back with <em>CREATE_FAILED</em> status and <em>Property IpProtocol cannot be empty</em> error. What I am doing wrong here?</p>