It looks like Rails was recently broken in Rawhide when activesupport
and activemodel 4.0.2 went out a couple days ago.
Here's the bug against activesupport:
https://bugzilla.redhat.com/1040214 . (Later I discovered that
activemodel has a similar issue.)
To see the problem, try "yum install rubygem-rails" on a Rawhide box.
Some of the gems require 4.0.1, and some require 4.0.2.
- Ken