Use simplejson first, and centralize import

simplejson is supposed to be faster:
http://stackoverflow.com/questions/712791/json-and-simplejson-module-differences-in-python

modules/aum/browser.py

@@ -24,12 +24,9 @@ import datetime
 import random
 import urllib
 from htmlentitydefs import codepoint2name
-try:
-    import json
-except ImportError:
-    import simplejson as json
 
 from weboob.tools.browser import BaseBrowser, BrowserIncorrectPassword, BrowserUnavailable
+from weboob.tools.json import json
 
 from weboob.capabilities.chat import ChatException, ChatMessage
 from weboob.capabilities.messages import CantSendMessage

modules/izneo/backend.py

@@ -19,14 +19,10 @@
 
 from __future__ import with_statement
 
-try:
-    import simplejson as json
-except ImportError:
-    import json
-
 import re
 
 from weboob.capabilities.gallery import ICapGallery, BaseGallery, BaseImage
+from weboob.tools.json import json
 from weboob.tools.backend import BaseBackend
 from weboob.tools.browser import BaseBrowser, BasePage
 

modules/mediawiki/browser.py

@@ -22,14 +22,9 @@ import urllib
 import datetime
 
 from weboob.tools.browser import BaseBrowser, BrowserIncorrectPassword
+from weboob.tools.json import json as simplejson
 from weboob.capabilities.content import Revision
 
-try:
-    import simplejson
-except ImportError:
-    # Python 2.6+ has a module similar to simplejson
-    import json as simplejson
-
 __all__ = ['MediawikiBrowser']
 
 

modules/radiofrance/browser.py

@@ -18,6 +18,7 @@
 # along with weboob. If not, see <http://www.gnu.org/licenses/>.
 
 from weboob.tools.browser import BaseBrowser, BasePage
+from weboob.tools.json import json
 from weboob.capabilities.video import BaseVideo
 from weboob.tools.browser.decorators import id2url
 
@@ -25,11 +26,6 @@ from StringIO import StringIO
 from time import time
 import re
 
-try:
-    import json
-except ImportError:
-    import simplejson as json
-
 try:
     from urlparse import parse_qs
 except ImportError:

modules/youtube/pages.py

@@ -18,14 +18,10 @@
 # along with weboob. If not, see <http://www.gnu.org/licenses/>.
 
 
-try:
-    import json
-except ImportError:
-    import simplejson as json
-
 import urllib
 
 from weboob.tools.browser import BasePage, BrokenPageError, BrowserIncorrectPassword
+from weboob.tools.json import json
 
 
 __all__ = ['LoginPage', 'LoginRedirectPage', 'ForbiddenVideo', 'ForbiddenVideoPage', \