old_contents: 
  """
  Metrics extensions for routes.
  
  """
  try:
      from microcosm_metrics.classifier import Classifier
  except ImportError:
      raise Exception("Route metrics require 'microcosm-metrics'")
  
  
  from microcosm_flask.audit import parse_response
  from microcosm_flask.errors import extract_status_code
  
  
  class StatusCodeClassifier(Classifier):
      """
      Label route results its status code.
  
      """
      def label_result(self, result):
          _, status_code = parse_response(result)
          return str(status_code)
  
      def label_error(self, error):
          status_code = extract_status_code(error)
          return str(status_code)
  
new_contents: """
  Metrics extensions for routes.
  
  """
  try:
      from microcosm_metrics.classifier import Classifier
  except ImportError:
      raise Exception("Route metrics require 'microcosm-metrics'")
  
  
  from microcosm_flask.audit import parse_response
  from microcosm_flask.errors import extract_status_code
  
  
  class StatusCodeClassifier(Classifier):
      """
      Label route results its status code.
  
      """
      def label_result(self, result):
          _, status_code = parse_response(result)
          return str(status_code)
  
      def label_error(self, error):
          status_code = extract_status_code(error)
          return str(status_code)
  
subject: Remove empty line