beets.logging exports NullHandler on python 2.6

NullHandler is not available in python 2.6. We backport it so the
importer log can use it for it is more convenient than guarding calls to
self.logger (see beets/importer.py)

beets/logging.py

@@ -92,3 +92,16 @@ if PY26:
         return logger
 
     my_manager.getLogger = new_getLogger
+
+
+# Offer NullHandler in Python 2.6 to reduce the difference with never versions
+if PY26:
+    class NullHandler(Handler):
+        def handle(self, record):
+            pass
+
+        def emit(self, record):
+            pass
+
+        def createLock(self):
+            self.lock = None