安装系统升级DNF插件失败.我想从25升级到26

#sudo dnf install dnf-plugin-system-upgrade
Repository updates is listed more than once in the configuration
Repository updates-debuginfo is listed more than once in the configuration
Repository updates-source is listed more than once in the configuration
Repository fedora is listed more than once in the configuration
Repository fedora-debuginfo is listed more than once in the configuration
Repository fedora-source is listed more than once in the configuration
Repository fzug-free is listed more than once in the configuration
Repository fzug-free-source is listed more than once in the configuration
Repository fzug-nonfree is listed more than once in the configuration
Repository fzug-nonfree-source is listed more than once in the configuration
Failed to synchronize cache for repo 'fedora'，禁用。
Failed to synchronize cache for repo 'fedora-steam'，禁用。
Failed to synchronize cache for repo 'phnxrbrn-evopop'，禁用。
Failed to synchronize cache for repo 'updates'，禁用。
Failed to synchronize cache for repo 'google-chrome'，禁用。
Failed to synchronize cache for repo 'google-chrome-beta'，禁用。
上次元数据过期检查：0:02:07 前，执行于 Sat Feb 16 07:09:31 2019。
没有可用软件包 dnf-plugin-system-upgrade。
错误：没有任何匹配
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按照更新步骤:
1、更新系统
# dnf update --refresh
2、安装插件
# dnf install dnf-plugin-system-upgrade
3、下载Fedora24版本的更新包
# dnf system-upgrade download --releasever=24 --allowerasing
吧友谁知道为什么的fedaora25 到第2步始终失败?怎么也安装不了dnf 插件....