old_contents: """ Username to UUID
   Converts a Minecraft username to it's UUID equivalent.
  
  Uses the official Mojang API to fetch player data.
  """
  import http.client
  import json
  
  
  class UsernameToUUID:
      def __init__(self, username):
          self.username = username
  
      def get_uuid(self, timestamp=None):
          """
            Get the UUID of the player.
  
            Parameters
            ----------
            timestamp : long integer
                The time at which the player used this name, expressed as a Unix timestamp.
          """
          get_args = "" if timestamp is None else "?at=" + str(timestamp)
  
          http_conn = http.client.HTTPSConnection("api.mojang.com");
          http_conn.request("GET", "/users/profiles/minecraft/" + self.username + get_args,
              headers={'User-Agent':'Minecraft Username -> UUID', 'Content-Type':'application/json'});
          response = http_conn.getresponse().read().decode("utf-8")
  
          if (not response and timestamp is None): # No response & no timestamp
              return self.get_uuid(0) # Let's retry with the Unix timestamp 0.
          if (not response): # No response (player probably doesn't exist)
              return ""
  
          json_data = json.loads(response)
          uuid = json_data['id']
  
          return uuid
  
new_contents: """ Username to UUID
   Converts a Minecraft username to it's UUID equivalent.
  
  Uses the official Mojang API to fetch player data.
  """
  import http.client
  import json
  
  
  class UsernameToUUID:
      def __init__(self, username):
          self.username = username
  
      def get_uuid(self, timestamp=None):
          """
            Get the UUID of the player.
  
            Parameters
            ----------
            timestamp : long integer
                The time at which the player used this name, expressed as a Unix timestamp.
          """
          get_args = "" if timestamp is None else "?at=" + str(timestamp)
  
          http_conn = http.client.HTTPSConnection("api.mojang.com");
          http_conn.request("GET", "/users/profiles/minecraft/" + self.username + get_args,
              headers={'User-Agent':'Minecraft Username -> UUID', 'Content-Type':'application/json'});
          response = http_conn.getresponse().read().decode("utf-8")
  
          if (not response and timestamp is None): # No response & no timestamp
              return self.get_uuid(0) # Let's retry with the Unix timestamp 0.
          if (not response): # No response (player probably doesn't exist)
              return ""
  
          json_data = json.loads(response)
          try:
              uuid = json_data['id']
          except KeyError as e:
              print("KeyError raised:", e);
  
          return uuid
  
subject: Improve robustness: surround the 'id' fetch from result array with a try clause.