offlineimap/utils files singleton-comparison

This patch change these errors in the utils folder

C0121: Comparison to None should be 'expr is None' (singleton-comparison)
C0121: Comparison to None should be 'expr is not None' (singleton-comparison)

offlineimap/utils/const.py

@@ -15,7 +15,7 @@ class ConstProxy():
 
     def __getattr__(self, name):
         src = self.__dict__['__source']
-        if src == None:
+        if src is None:
             raise ValueError("using non-initialized ConstProxy() object")
         return copy.deepcopy(getattr(src, name))
 
@@ -29,6 +29,6 @@ class ConstProxy():
 
     def set_source(self, source):
         """ Sets source object for this instance. """
-        if (self.__dict__['__source'] != None):
+        if (self.__dict__['__source'] is not None):
             raise ValueError("source object is already set")
         self.__dict__['__source'] = source

offlineimap/utils/distro.py

@@ -86,7 +86,7 @@ def get_os_sslcertfile():
     """
 
     l = get_os_sslcertfile_searchpath()
-    if l == None:
+    if l is None:
         return None
 
     for f in l: