yum.cronからのエラーメッセージ

自宅のサーバはミッションクリティカルでも何でもないので、パッケージ管理は毎夜cronにお任せ。
で、そのcronからエラーメールが飛んできた。ちょっと長いけど以下のような内容。

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 229, in user_main
errcode = main(args)
File "/usr/share/yum-cli/yummain.py", line 104, in main
result, resultmsgs = base.doCommands()
File "/usr/share/yum-cli/cli.py", line 343, in doCommands
return self.yum_cli_commands[self.basecmd].doCommand(self, self.basecmd, self.extcmds)
File "/usr/share/yum-cli/yumcommands.py", line 645, in doCommand
return base.doShell()
File "/usr/share/yum-cli/cli.py", line 284, in doShell
yumshell.script()
File "/usr/share/yum-cli/shell.py", line 78, in script
self.onecmd(line)
File "/usr/lib/python2.4/cmd.py", line 219, in onecmd
return func(arg)
File "/usr/share/yum-cli/shell.py", line 165, in do_ts
self.do_transaction(line)
File "/usr/share/yum-cli/shell.py", line 191, in do_transaction
return self.do_run('')
File "/usr/share/yum-cli/shell.py", line 325, in do_run
(code, msgs) = self.base.buildTransaction()
File "/usr/lib/python2.4/site-packages/yum/__init__.py", line 647, in buildTransaction
(rescode, restring) = self.resolveDeps()
File "/usr/lib/python2.4/site-packages/yum/depsolve.py", line 704, in resolveDeps
for po, dep in self._checkFileRequires():
File "/usr/lib/python2.4/site-packages/yum/depsolve.py", line 939, in _checkFileRequires
if not self.tsInfo.getOldProvides(filename) and not self.tsInfo.getNewProvides(filename):
File "/usr/lib/python2.4/site-packages/yum/transactioninfo.py", line 414, in getNewProvides
for pkg, hits in self.pkgSack.getProvides(name, flag, version).iteritems():
File "/usr/lib/python2.4/site-packages/yum/packageSack.py", line 300, in getProvides
return self._computeAggregateDictResult("getProvides", name, flags, version)
File "/usr/lib/python2.4/site-packages/yum/packageSack.py", line 470, in _computeAggregateDictResult
sackResult = apply(method, args)
File "/usr/lib/python2.4/site-packages/yum/sqlitesack.py", line 861, in getProvides
return self._search("provides", name, flags, version)
File "/usr/lib/python2.4/site-packages/yum/sqlitesack.py", line 43, in newFunc
return func(*args, **kwargs)
File "/usr/lib/python2.4/site-packages/yum/sqlitesack.py", line 837, in _search
for pkg in self.searchFiles(name, strict=True):
File "/usr/lib/python2.4/site-packages/yum/sqlitesack.py", line 43, in newFunc
return func(*args, **kwargs)
File "/usr/lib/python2.4/site-packages/yum/sqlitesack.py", line 586, in searchFiles
self._sql_pkgKey2po(rep, cur, pkgs)
File "/usr/lib/python2.4/site-packages/yum/sqlitesack.py", line 470, in _sql_pkgKey2po
pkg = self._packageByKey(repo, ob['pkgKey'])
File "/usr/lib/python2.4/site-packages/yum/sqlitesack.py", line 413, in _packageByKey
po = self.pc(repo, cur.fetchone())
File "/usr/lib/python2.4/site-packages/yum/sqlitesack.py", line 68, in __init__
self._read_db_obj(db_obj)
File "/usr/lib/python2.4/site-packages/yum/sqlitesack.py", line 94, in _read_db_obj
setattr(self, item, _share_data(db_obj[item]))
TypeError: unsubscriptable object

ちょうどPythonの勉強を始めた事もあって、何とかエラーの内容は想像がついた。単純にアップデートが出来ていない模様。
検索してみたところ、以下の記事にたどり着いた。
CentOS 5 の yum に失敗 (TypeError: unsubscriptable object)
以下のコマンド実行後にyum updateしたら、無事動くようになった。

# yum clean metadata

こうなった原因が気になるところ(・x・ ).o0○