bug#8847: New format/layout for byte-compiled files in python >= 3.2 penalizes automake support

[Stefano Lattarini]

Python 3.2 has changed the way in which byte-compiled files are stored
and searched for, introducing the new concept of a cache directory
`__pycache__' where version-specific byte-compiled files can be stored,
for many different python versions and implementations at once:

 <http://www.python.org/dev/peps/pep-3147/>

This bit (from the "Proposal" section) is mostly relevant to us:

 ``.pyc file outside of __pycache__ will only be imported if the .py
    source file is missing.''

This means that the byte-compiled files installed by the Python support in
Automake will not be used by newer (>= 3.2) python versions :-(

Luckily for us, this is "just" an optimization issue, not a correctness one:
python 3.2 and later will simply use the *.py files installed by automake,
the only downside being that it will have to recompile them on the fly each
time.

Nonetheless, I think this issue should be fixed in automake 1.12.

Regards,
  Stefano