Hi Mike,
I have run into issues while trying to build RPM as per gsutil/README.pkg and further analysis showed that it's distribution file issue.
Starting with gsutil 3.19 files gsutil/MANIFEST.in and gsutil/setup.py are no longer from gsutil svn but instead from boto git, so gsutil RPM packaging now is clearly broken (I didn't check for other files possibly not matching gsutil svn, I just stepped back to gsutil 3.18 until RPM packaging issues will be resolved).
Also, for Scientific Linux 6.3 (i.e. the same for RHEL 6.3), one has to fix path to Python egg file and include several Python-compiled files to get over "installed but not included into rpm" issue (I attached a quick patch, though you might find a better way to fix this).
Hope this info will help you to sort everything out. Thanks for your help and great product!
Regards,
Danylo