Added some exceptions and fleshed out some docstrings

Github/exceptions.py

@@ -1,9 +1,52 @@
 #== exceptions.py ==#
 
+import datetime
+
 __all__ = (
     'APIError',
+    'Ratelimited'
 )
 
 class APIError(Exception):
-    """Base level exceptions raised by errors related to any API request or call"""
-    pass
+    """Base level exceptions raised by errors related to any API request or call."""
+    pass
+
+class Ratelimited(APIError):
+    """Raised when the ratelimit from Github is reached or exceeded."""
+    def __init__(self, reset_time: datetime.datetime):
+        formatted = reset_time.strftime(r"%H:%M:%S %A, %d %b")
+        msg = "We're being ratelimited, wait until {}.\nAuthentication raises the ratelimit.".format(formatted)
+        super().__init__(msg)
+
+class WillExceedRatelimit(APIError):
+    """Raised when the library predicts the call will exceed the ratelimit, will abort the call by default."""
+    def __init__(self, response, count):
+        msg = 'Performing this action will exceed the ratelimit, aborting.\n{} remaining available calls, calls to make: {}'
+        msg = msg.format(response.header['X-RateLimit-Remaining'], count)
+        super().__init__(msg)
+
+class UserNotFound(APIError):
+    def __init__(self):
+        msg = 'User not found'
+        super().__init__(msg)
+
+class OrganizationNotFound(APIError):
+    def __init__(self):
+        msg = 'Organization not found'
+        super().__init__(msg)
+
+class RepositoryNotFound(APIError):
+    def __init__(self):
+        msg = 'Repository not found'
+        super().__init__(msg)
+
+class NoAuthProvided(APIError):
+    """Raised when no proper authorization or invalid authorization is given to the client"""
+    def __init__(self):
+        msg = 'Without authorization, this client doesn\'t have it\'s own repository'
+        super().__init__(msg)
+
+class ObjectNotFound(APIError):
+    def __init__(self):
+        msg = 'The requested object was not found, ensure spelling is correct before proceeding'
+        super().__init__(msg)