old_contents: try:
      import simplejson as json
  except ImportError:
      import json
  
  
  def deserialize(cassette_string):
      return json.loads(cassette_string)
  
  
  def serialize(cassette_dict):
      error_message = (
          "Does this HTTP interaction contain binary data? "
          "If so, use a different serializer (like the yaml serializer) "
          "for this request?"
      )
  
      try:
          return json.dumps(cassette_dict, indent=4)
      except UnicodeDecodeError as original:  # py2
          raise UnicodeDecodeError(
              original.encoding,
              b"Error serializing cassette to JSON",
              original.start,
              original.end,
              original.args[-1] + error_message
          )
      except TypeError as original:  # py3
          raise TypeError(error_message)
  
new_contents: try:
      import simplejson as json
  except ImportError:
      import json
  
  
  def deserialize(cassette_string):
      return json.loads(cassette_string)
  
  
  def serialize(cassette_dict):
      error_message = (
          "Does this HTTP interaction contain binary data? "
          "If so, use a different serializer (like the yaml serializer) "
          "for this request?"
      )
  
      try:
          return json.dumps(cassette_dict, indent=4)
      except UnicodeDecodeError as original:  # py2
          raise UnicodeDecodeError(
              original.encoding,
              b"Error serializing cassette to JSON",
              original.start,
              original.end,
              original.args[-1] + error_message
          )
      except TypeError:  # py3
          raise TypeError(error_message)
  
subject: Fix flake8 in python3