This appears to have been fixed in 2.5 and trunk.  2.4.x is old and in
security fixes only mode so I wouldn't expect to see this in any
official 2.4.x source tree released in the future unless the bdfl
changes his mind on that.  here's the patch to fix it (as described in
the email thread mentioned earlier):

Index: Lib/os.py
===================================================================
--- Lib/os.py   (revision 60877)
+++ Lib/os.py   (working copy)
@@ -351,8 +351,8 @@
 
 __all__.extend(["execl","execle","execlp","execlpe","execvp","execvpe"])
 
+import errno
 def _execvpe(file, args, env=None):
-    from errno import ENOENT, ENOTDIR
 
     if env is not None:
         func = execve
@@ -379,7 +379,7 @@
             func(fullname, *argrest)
         except error, e:
             tb = sys.exc_info()[2]
-            if (e.errno != ENOENT and e.errno != ENOTDIR
+            if (e.errno != errno.ENOENT and e.errno != errno.ENOTDIR
                 and saved_exc is None):
                 saved_exc = e
                 saved_tb = tb