Actually, I saw this as a bug with urllib.urlopen and urllib2 had
exhibited proper behaviour previously. Now, both behaviour will be
consistent now.

But, you are right that an *incorrect* usage of urllib.urlopen would
break in 2.7.2. 

If we need to be lenient on that incorrect usage, then this change can
be there in 3.x series, because of urllib.request.urlopen would be
interface which users will be using and it can be reverted from 2.7.

Personally, I am +/- 0 on reverting this in 2.7. Initially, I saw this
as a bug, but later when I added tests for ValueError and checkedin,
I realized that it can break some incorrect usages, as you say.