Was seeing this:
$ rbenv install 2.2.1
Downloading ruby-2.2.1.tar.gz...
-> http://dqw8nmjcqpjn7.cloudfront.net/5a4de38068eca8919cb087d338c0c2e3d72c9382c804fb27ab746e6c7819ab28
Installing ruby-2.2.1...
BUILD FAILED (OS X 10.10.2 using ruby-build 20150413)
Inspect or clean up the working tree at /var/folders/6s/3js1zy6j2bsc707nynpqx9fw0000gn/T/ruby-build.20150813104612.70538
Results logged to /var/folders/6s/3js1zy6j2bsc707nynpqx9fw0000gn/T/ruby-build.20150813104612.70538.log
Last 10 log lines:
Accept-Ranges: bytes
Server: AmazonS3
Age: 64584
X-Cache: Hit from cloudfront
Via: 1.1 5e323b6c052608df0aafd791e1a14e3b.cloudfront.net (CloudFront)
X-Amz-Cf-Id: f_QdMk0nLFIkoE6VRw_5nud5mmZlyejVVmz3EmYoRs_pq_htYPhVTQ==
/var/folders/6s/3js1zy6j2bsc707nynpqx9fw0000gn/T/ruby-build.20150813104612.70538/ruby-2.2.1 /var/folders/6s/3js1zy6j2bsc707nynpqx9fw0000gn/T/ruby-build.20150813104612.70538 ~/Projects/CrowdFlower/flower_ai
configure: error: expected an absolute directory name for --prefix: readline)
make: *** No targets specified and no makefile found. Stop.
Wound up having to following dirs here. Namely:
$ RUBY_CONFIGURE_OPTS=--with-readline-dir=`brew --prefix readline` rbenv install 2.2.1