Fix authentication exception not declared

Closes #12

humble_api/exceptions/humble_authentication_exception.py

@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+from .humble_response_exception import HumbleResponseException
+
+__license__ = "MIT"
+
+
+class HumbleAuthenticationException(HumbleResponseException):
+    """
+        Authentication failed due to a rejected authentication cookie
+    """
+
+    def __init__(self, *args, **kwargs):
+        """
+            Parameterized constructor for the HumbleAuthenticationException.
+            :param list args: (optional) Extra positional args to pass to the request.
+            :param dict kwargs: (optional) Extra keyword args to pass to the request.
+        """
+
+        super(HumbleAuthenticationException, self).__init__(*args, **kwargs)

humble_api/humble_api.py

@@ -6,6 +6,7 @@
 import requests
 from .exceptions.humble_response_exception import HumbleResponseException
 from .exceptions.humble_parse_exception import HumbleParseException
+from .exceptions.humble_authentication_exception import HumbleAuthenticationException
 
 __author__ = "Joel Pedraza"
 __copyright__ = "Copyright 2014, Joel Pedraza"