'Copy kernel/initrd to destdir with (optional) newfile prefix'

def copy_boot_files(self, distro, destdir, prefix=None):

    if (not os.path.exists(distro.kernel)):
        utils.die(self.logger, ('path    does    not    exist:    %s' % distro.kernel))
    if (not os.path.exists(distro.initrd)):
        utils.die(self.logger, ('path    does    not    exist:    %s' % distro.initrd))
    if (prefix is None):
        shutil.copyfile(distro.kernel, os.path.join(destdir, ('%s' % os.path.basename(distro.kernel))))
        shutil.copyfile(distro.initrd, os.path.join(destdir, ('%s' % os.path.basename(distro.initrd))))
    else:
        shutil.copyfile(distro.kernel, os.path.join(destdir, ('%s.krn' % prefix)))
        shutil.copyfile(distro.initrd, os.path.join(destdir, ('%s.img' % prefix)))
