'return a path object pointing to source code (note that it
might not point to an actually existing file).'

@property
def path(self):

    try:
        p = py.path.local(self.raw.co_filename)
        if (not p.check()):
            raise OSError('py.path    check    failed.')
    except OSError:
        p = self.raw.co_filename
    return p
