Actually remove directories from sys.path if they do not exist; the intent

is to avoid as many stat() calls as we can.

Lib/site.py

@@ -79,6 +79,10 @@ del m
 L = []
 dirs_in_sys_path = {}
 for dir in sys.path:
+    # Filter out paths that don't exist, but leave in the empty string
+    # since it's a special case.
+    if dir and not os.path.isdir(dir):
+        continue
     dir, dircase = makepath(dir)
     if not dirs_in_sys_path.has_key(dircase):
         L.append(dir)