docs: CodingGuidelines: remove duplicate content

Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

docs/CodingGuidelines.rst

@@ -13,57 +13,6 @@ This document contains assorted guidelines for programmers that want
 to hack OfflineIMAP.
 
 
-------------------
-Exception handling
-------------------
-
-OfflineIMAP on many occasions re-raises various exceptions and often
-changes exception type to `OfflineImapError`.  This is not a problem
-per se, but you must always remember that we need to preserve original
-tracebacks.  This is not hard if you follow these simple rules.
-
-For re-raising original exceptions, just use::
-
-  raise
-
-from inside your exception handling code.
-
-If you need to change exception type, or its argument, or whatever,
-use this three-argument form::
-
-  raise YourExceptionClass(argum, ents), None, sys.exc_info()[2]
-
-In this form, you're creating an instance of new exception, so ``raise``
-will deduce its ``type`` and ``value`` parameters from the first argument,
-thus the second expression passed to ``raise`` is always ``None``.
-And the third one is the traceback object obtained from the thread-safe
-``exc_info()`` function.
-
-In fact, if you hadn't already imported the whole ``sys`` module, it will
-be better to import just ``exc_info()``::
-
-  from sys import exc_info
-
-and raise like this::
-
-  raise YourExceptionClass(argum, ents), None, exc_info()[2]
-
-since this is the historically-preferred style in the OfflineIMAP code.
-.. -*- coding: utf-8 -*-
-.. _OfflineIMAP: https://github.com/OfflineIMAP/offlineimap
-.. _OLI_git_repo: git://github.com/OfflineIMAP/offlineimap.git
-
-=================================
-Coding guidelines for OfflineIMAP
-=================================
-
-.. contents::
-.. .. sectnum::
-
-This document contains assorted guidelines for programmers that want
-to hack OfflineIMAP.
-
-
 ------------------
 Exception handling
 ------------------