Apparently this may have become Windows-specific at some point. I can't reproduce under Linux with Python 2.6.5, 2.7 or 3.2.

I get a strange warning with -v under 2.7, though:

$ touch b.py && ~/cpython/27/python -v a.py 2>&1 | grep b.py
# /home/antoine/py3k/__svn__/b.pyc has bad mtime
import b # from /home/antoine/py3k/__svn__/b.py
# wrote /home/antoine/py3k/__svn__/b.pyc

("bad mtime"??)