Yum fails with error "TypeError: iterable argument required"

Issue

• yum fails to update.
• Following messages provided from yum update:

# yum update  
Loaded plugins: rhnplugin, security  
Traceback (most recent call last):  
 File "/usr/bin/yum", line 29, in ?  
   yummain.user\_main(sys.argv[1:], exit\_code=True)  
 File "/usr/share/yum-cli/yummain.py", line 309, in user_main  
   errcode = main(args)  
 File "/usr/share/yum-cli/yummain.py", line 178, in main  
   result, resultmsgs = base.doCommands()  
 File "/usr/share/yum-cli/cli.py", line 345, in doCommands  
   self._getTs(needTsRemove)  
 File "/usr/lib/python2.4/site-packages/yum/depsolve.py", line 101, in _getTs  
   self.\_getTsInfo(remove\_only)  
 File "/usr/lib/python2.4/site-packages/yum/depsolve.py", line 112, in _getTsInfo  
   pkgSack = self.pkgSack  
 File "/usr/lib/python2.4/site-packages/yum/\_\_init\_\_.py", line 661, in <lambda>  
   pkgSack = property(fget=lambda self: self._getSacks(),  
 File "/usr/lib/python2.4/site-packages/yum/\_\_init\_\_.py", line 501, in _getSacks  
   self.repos.populateSack(which=repos)  
 File "/usr/lib/python2.4/site-packages/yum/repos.py", line 260, in populateSack  
   sack.populate(repo, mdtype, callback, cacheonly)  
 File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 187, in populate  
   xml = repo\_get\_function()  
 File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1543, in getPrimaryXML  
   return self.retrieveMD('primary')  
 File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1484, in retrieveMD  
   return self._retrieveMD(mdtype)  
 File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1524, in _retrieveMD  
   cache=self.http_caching == 'all')  
 File "/usr/lib/yum-plugins/rhnplugin.py", line 308, in _getFile  
   start, end, copy_local, checkfunc, text, reget, cache)  
 File "/usr/lib/yum-plugins/rhnplugin.py", line 401, in _noExceptionWrappingGet  
   timeout=self.timeout  
 File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 934, in urlgrab  
   return self._retry(opts, retryfunc, url, filename)  
 File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 852, in _retry  
   r = apply(func, (opts,) + args, {})  
 File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 920, in retryfunc  
   fo = URLGrabberFileObject(url, filename, opts)  
 File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 1008, in \_\_init\_\_  
   self.\_do\_open()  
 File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 1091, in \_do\_open  
   fo, hdr = self.\_make\_request(req, opener)  
 File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 1200, in \_make\_request  
   fo = opener.open(req)  
 File "/usr/lib64/python2.4/urllib2.py", line 358, in open  
   response = self._open(req, data)  
 File "/usr/lib64/python2.4/urllib2.py", line 376, in _open  
   '_open', req)  
 File "/usr/lib64/python2.4/urllib2.py", line 337, in \_call\_chain  
   result = func(\*args)  
 File "/usr/lib64/python2.4/urllib2.py", line 573, in <lambda>  
   lambda r, proxy=url, type=type, meth=self.proxy_open: \\  
 File "/usr/lib64/python2.4/urllib2.py", line 580, in proxy_open  
   if '@' in host:  
 TypeError: iterable argument required