While upgrading a CentOS 4.5 to CentOS 5.*, yum starts to fail with

/usr/lib/python2.4/site-packages/_sqlitecache.so: undefined symbol: g_assert_warning

Please install a package which provides this module, or
verify that the module is installed correctly.

It’s possible that the above module doesn’t match the
current version of Python, which is:
2.4.3 (#1, May 24 2008, 13:47:28)
[GCC 4.1.2 20070626 (Red Hat 4.1.2-14)]

Reason

The reason was that the glib2 package hadn’t been updated at the same time as the yum and python packages, since they only required glib2 and not a specific version.

Solution

So the solution was to upgrade glib2 manually with the rpm command after which yum worked again.

I was trying to have the yum cache on a lustre mount so it could be shared amongst several machines to save on external bandwidth, but got the message that
_sqlite.OperationalError: database is locked

It also happens with an nfs mounted directory.

Solution

For lustre solution was to mount with localflock, for nfs the solutions is to make sure the nfslock service is running.