im trying to reposync redhat5 repos from a new deployed system of redhat 7.3 and its result with the below error.
on my redhat 6 its works.
what could be the problem?

yum repolist

Loaded plugins: langpacks, product-id, search-disabled-repos, subscription-manager
Traceback (most recent call last):
File "/bin/yum", line 29, in
yummain.user_main(sys.argv[1:], exit_code=True)
File "/usr/share/yum-cli/yummain.py", line 370, in user_main
errcode = main(args)
File "/usr/share/yum-cli/yummain.py", line 179, in main
result, resultmsgs = base.doCommands()
File "/usr/share/yum-cli/cli.py", line 573, in doCommands
return self.yum_cli_commands[self.basecmd].doCommand(self, self.basecmd, self.extcmds)
File "/usr/share/yum-cli/yumcommands.py", line 2153, in doCommand
base.repos.populateSack()
File "/usr/lib/python2.7/site-packages/yum/repos.py", line 380, in populateSack
sack._retrieve_async(repo, data)
File "/usr/lib/python2.7/site-packages/yum/yumRepo.py", line 187, in _retrieve_async
repo._retrieveMD(mydbtype, async=True, failfunc=None)
File "/usr/lib/python2.7/site-packages/yum/yumRepo.py", line 1851, in _retrieveMD
text = "%s/%s" % (self.ui_id, mdtype)
File "/usr/lib/python2.7/site-packages/yum/yumRepo.py", line 437, in _ui_id
ret += str(self.yumvar[var])
KeyError: 'basearc'