ImportError: cannot import name exception2msg

hi, I encountered this error while installing yum. Could you help me ?

**Traceback (most recent call last):
  File "/usr/bin/yum", line 28, in <module>
    import yummain
  File "/usr/share/yum-cli/yummain.py", line 32, in <module>
    from yum.i18n import utf8_width, exception2msg
ImportError: cannot import name exception2msg**
