Thanks, but

-----> Compiling Ruby/Rack
Could not get translated url, exited with: DEPENDENCY_MISSING_IN_MANIFEST: https://s3-external-1.amazonaws.com/heroku-buildpack-ruby/ruby-2.1.5.tgz


When I try the s3 URL in a browser I see

<Error>
<Code>AccessDenied</Code>
<Message>Access Denied</Message>
<RequestId>0A8DA74BC355E61E</RequestId>
<HostId>
OAHOWhKzXcaZmIwMFTYXJmaLvzvyC5HxNRORtzEPvOZ/TFjWMvr8foQTqSuPYPxp
</HostId>
</Error>