ClassCastException requiring minitest with JRuby 9000 #2570
Description
I am encountering a ClassCastException when attempting to require 'minitest' on JRuby master:
$ ruby -v
jruby 9.0.0.0-SNAPSHOT (2.2.0p0) 2015-02-05 cad0d25 OpenJDK 64-Bit Server VM 24.75-b04 on 1.7.0_75-b13 +jit [linux-amd64]
$ ruby -e "gem 'minitest', '5.5.1'; require 'minitest'"
LoadError: load error: minitest -- java.lang.ClassCastException: java.lang.String cannot be cast to org.jruby.runtime.builtin.IRubyObject
require at org/jruby/RubyKernel.java:964
require at /home/philr/.rvm/rubies/jruby-head/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:54
__script__ at -e:1
Judging by Travis CI builds, this issue seems to have started somewhere between a10fccc and c804f97.