rails/rails — pull request #9908 by jacobo (2013-03-25 02:09:07+00:00)
Title: Could not find gem 'arel (~> 3.0.2) ruby', which is required by gem 'rails (>= 0) ruby', in any of the sources.

Seems to be a problem bundling current rail master (7a32c6300c2b11dc1660338535c653a0132df196)

workaround is removing the arel requirement from Gemfile

seems this is because rails gemspec specified arel and master of arel are incompatible version:

Bundler could not find compatible versions for gem "arel":
In Gemfile:
rails (>= 0) ruby depends on
arel (~> 3.0.2) ruby

arel (4.0.0.beta2.20130314230643)

https://github.com/carlhuda/bundler/issues/2419