不能使用任何yum命令“全局名称”IncrementalDecoder“未定义”

每次我编写任何相关的yum命令时，在我的CentOS 6.9 64位系统上，答案是：

Traceback (most recent call last): File "/usr/bin/yum", line 29, in <module> yummain.user_main(sys.argv[1:], exit_code=True) File "/usr/share/yum-cli/yummain.py", line 298, in user_main errcode = main(args) File "/usr/share/yum-cli/yummain.py", line 115, in main base.getOptionsConfig(args) File "/usr/share/yum-cli/cli.py", line 229, in getOptionsConfig self.conf File "/usr/lib/python2.6/site-packages/yum/__init__.py", line 911, in <lambda> conf = property(fget=lambda self: self._getConfig(), File "/usr/lib/python2.6/site-packages/yum/__init__.py", line 335, in _getConfig startupconf.pluginconfpath,disabled_plugins,enabled_plugins) File "/usr/lib/python2.6/site-packages/yum/__init__.py", line 564, in doPluginSetup plugin_types, confpath, disabled_plugins, enabled_plugins) File "/usr/lib/python2.6/site-packages/yum/plugins.py", line 159, in __init__ self._importplugins(types) File "/usr/lib/python2.6/site-packages/yum/plugins.py", line 211, in _importplugins nxt = ' ' * (utf8_width(key) - 2) + ': ' File "/usr/lib/python2.6/site-packages/yum/i18n.py", line 218, in utf8_width for (ucs, bytes) in __utf8_iter_ucs(msg): File "/usr/lib/python2.6/site-packages/yum/i18n.py", line 174, in __utf8_iter_ucs for byte0 in uiter: File "/usr/lib/python2.6/site-packages/yum/i18n.py", line 170, in __utf8_iter_ints for byte in to_utf8(msg): File "/usr/lib/python2.6/site-packages/yum/i18n.py", line 436, in to_utf8 obj = obj.encode('utf-8', errors) File "/usr/lib64/python2.6/encodings/__init__.py", line 120, in search_function entry = getregentry() File "/usr/lib64/python2.6/encodings/utf_8.py", line 39, in getregentry incrementaldecoder=IncrementalDecoder, NameError: global name 'IncrementalDecoder' is not defined 

百胜清理所有，并删除并重新安装百胜没有解决问题。

任何提示？

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