20 upgrade 21 error help!

error code:
导入 GPG key 0x95A43F54:
用户ID : "Fedora (21) <fedora@fedoraproject.org>"
指纹 : 6596 b8fb abda 5227 a9c5 b59e 89ad 4e87 95a4 3f54
软件包 : fedora-release-20-1.noarch (@koji-override-0/$releasever)
来自 : /etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-21-x86_64
testing upgrade transaction
rpm transaction 100% [=========================================================]
rpm install 100% [=============================================================]
setting up system for upgrade
Traceback (most recent call last):
File "/usr/bin/fedup-cli", line 291, in <module>
main(args)
File "/usr/bin/fedup-cli", line 225, in main
prep_boot(kernel, initrd)
File "/usr/lib/python2.7/site-packages/fedup/sysprep.py", line 168, in prep_boot
customize_initrd(initrd)
File "/usr/lib/python2.7/site-packages/fedup/sysprep.py", line 136, in customize_initrd
newimg = boot.Initramfs(initrd)
File "/usr/lib/python2.7/site-packages/fedup/boot.py", line 62, in __init__
self._compression = detect_compression(self.open())
File "/usr/lib/python2.7/site-packages/fedup/boot.py", line 68, in open
fobj = Popen(cmd, stdout=PIPE, stderr=PIPE).stdout
File "/usr/lib64/python2.7/subprocess.py", line 711, in __init__
errread, errwrite)
File "/usr/lib64/python2.7/subprocess.py", line 1308, in _execute_child
raise child_exception
OSError: [Errno 2] No such file or directory
[root@localhost shi]#
thank you