As discussed in email thread:
http://www.gossamer-threads.com/lists/python/dev/497487

In particular, there are three specific reasons for not having it. I expect 
these reasons to translate to a larger number of specific reasons as 
more people use python 2.5.

1) Ralf's software gets a flood of ImportWarnings
2) Twisted's plugin system uses a directory named "twisted" without an 
__init__.py in it on the python path to store plugins in. Therefore, 
anybody running (importing) twisted will produce annoying warnings.
3) I have a directory in my homedir called "readline".

Quoted from my email:
I just found another reason to dislike the warnings: my homedir on 
one machine has a lot of random directories in it. One of them is 
named "readline". Every time I run python 2.5, it now helpfully notes: 
sys:1: ImportWarning: Not importing directory 'readline': missing 
__init__.py 

It used to be the case that it was very unlikely that running python 
in your homedir would cause issues. Even though the current directory 
is on the default pythonpath, you needed to have either a file ending 
in .py or a directory with an __init__.py with the same name as a 
python module to cause problems. And that is generally unlikely to 
happen. Now, however, you get warnings just by having _any_ directory 
in your CWD with the same name as a python module. That's much 
more 
likely to happen; I can't be the only one who will have this issue. 



Suggested solution: Remove ImportWarning, and make the ImportError 
message say:
>> ImportError: No module named mypackage.foo 
>> Note that subdirectories are searched for imports only if they 
contain an 
>> __init__.py file: http://www.python.org/doc/essays/packages.html 

I really think this should be addressed before 2.5 is released.

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I have submitted a patch (#1515361) that causes
find_module() to only generate these warnings if the import
fails.

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The warning is now off by default.  The behaviour will be
revisited for 2.6.  See PEP 361 for 2.6.