python-dateutil will be updated to version 2.x and there may be changes that affect this package. If python-mwlib will work with the newer python-dateutil, you can safely close this bug. If python-mwlib really does require python-dateutil 1.5, please use Requires: python-dateutil15 for Fedora versions of the package until it can be updated.
I tried to turn on the test suite in %check. Unfortunately it fails, in some date parsing tests. Interestingly, it fails in the same way with python-dateutil15 and python-dateutil-2.2 and python-dateutil-2.4, so the issue, whatever it is seems unrelated to the dateutil upgrade. I'll open a separate bug to discuss the testsuite issues.
OK, it seems that mwlib works fine with any dateutil version.