root use of yum (given "umask 077") causes build trouble

FYI,

[cc'ing the yum list, because yum may want to make the permissions
 of certain files it creates be independent of root's umask ]

When I do things as root, I have umask set to 077.
That appears to have led yum to set the permissions on all files in
/var/lib/yum/rpmdb-indexes/ to -rw-------.
That in turn makes commands run by non-root like "yum info libvirt" fail,
and it also makes libguestfs' build process fail like this:

    febootstrap: external python program failed, see earlier error messages

The previous error it's referring to appears to be this:

    IOError: [Errno 13] Permission denied: '//var/lib/yum/rpmdb-indexes/version'

I've just run this command (as root),

    chmod go+r /var/lib/yum/rpmdb-indexes/*

the libguestfs build was finally able to complete.
And "yum info ..." became usable again.

This is on Fedora 15.