use Cython.load_ipython_ext to simplify

IPython/extensions/cythonmagic.py

@@ -1,42 +1,41 b''
 # -*- coding: utf-8 -*-
 """
 The cython magic has been integrated into Cython itself, 
 which is now released in version 0.21.
 
 cf github `cython` organisation, `cython` repo, under the 
 file `Cython/Build/IpythonMagic.py`
 """
 #-----------------------------------------------------------------------------
 # Copyright (C) 2010-2011, IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 from __future__ import print_function
 
 try:
     import Cython
 except:
     Cython = None
 
 try:
     from Cython.Build.IpythonMagic import CythonMagics
 except :
     pass
 
 
 ## still load the magic in IPython 3.x, remove completely in future versions.
 def load_ipython_extension(ip):
     """Load the extension in IPython."""
     
     print("""The Cython magic has been move to the Cython package, hence """)
     print("""`%load_ext cythonmagic` is deprecated; Please use `%load_ext cython` instead.""")
     
     if Cython is None or tuple(map(int,Cython.__version__.split('.'))) < (0,21) : 
         print("You need Cython version >=0.21 to use the Cython magic")
         return 
-    if CythonMagics:
-        print("""\nThough, because I am nice, I'll still try to load it for you this time.""")
-        ip.register_magics(CythonMagics)
+    print("""\nThough, because I am nice, I'll still try to load it for you this time.""")
+    Cython.load_ipython_extension(ip)