Problem Running Test Suite

I was trying to run the test suite for 3.0.0.beta1. But, I kept
running into this error - "arel (~> 0.2.1, runtime) not found in any
of the sources".

And, I tried to google for arel 0.2.1. It seems like the latest
version is only 0.2.0 in Github.

Thank you.

$ gem list arel -r

*** REMOTE GEMS ***

arel (0.2.1)