Load an EC2 tag for the running instance & print it.

  :param str tagName: Name of the tag to read
  :param connection: Optional boto connection

def readMyEC2Tag(tagName, connection=None):
  """
  Load an EC2 tag for the running instance & print it.

  :param str tagName: Name of the tag to read
  :param connection: Optional boto connection
  """
  assert isinstance(tagName, basestring), ("tagName must be a string but is %r" % tagName)

  # Load metadata. if == {} we are on localhost
  # http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/AESDG-chapter-instancedata.html

  if not connection:
    # Assume AWS credentials are in the environment or the instance is using an IAM role
    connection = boto.ec2.connect_to_region(myRegion())

  return readInstanceTag(connection=connection,
                         instanceID=myInstanceID(),
                         tagName=tagName)