Short meesage for those who don't have time:
Software Collectoins for CentOS 6 are ready for upgrade from older rebuilds.
Now full story for those who care. Btw. this all is related to work done by SCLo SIG group that is part of CentOS (read more at http://wiki.centos.org/SpecialInterestGroup/SCLo).
A bit of history for beginning. Shortly after first RHSCL 1.0 release, CentOS rebuilds were prepared and since then they are available under:
http://mirror.centos.org/centos/6/SCL/x86_64/
However, keeping these rebuilds in sync with RHSCL content hasn't been easy task. With introduction of Java packages in collections, this task became even more tricky, which means these collections were not updated for long time. With that said, someone would expect there won't be problem with upgrade path, in other words that the new RPMs, that the SCLo SIG group is about to release, will update the older RPMs smoothly.
Well, not always. The original RPMs used ".el6.centos.alt" as %dist tag, while new builds use just ".el6" and that evolves in cases where python27-python-bson-2.5.2-4.el6.centos.alt.x86_64 > python27-python-bson-2.5.2-4.el6.x86_64, even if those packages have same Release tag in RPM SPEC. That obviously means the packages won't update smoothly.
Solution is quite simple in this case -- use higher Release in RPM SPEC. In some packages, this was already done, because some of the packages received update since original inclusion. In other cases we solve it by adding ".scX" (X is number) suffix to the Release tag. The ".scX" was chosen deliberately since ".scX.el6" is higher (alphabetically) than .el6.
Btw. for cases we need to build package more times before final build (bootstraping), we use suffix ".bsX", which means we can build package without any Release suffix in the end, because ".bsX.el6" < ".el6".
Anyway, this post was meant to let you know that upgrading of el6 packages from originally built RPMs is something we care about.
To verify it works, I've installed all the packages from original repository, then ran "yum update" and that evolved in proper update of all packages. I took that as proof it should work fine in your case as well. If there are still some issues, let us know.
Enjoy Software Collections on CentOS!