KeyError message renders String keys as Symbols

[olleolleolle]

Environment

➜  ~ ruby -v
jruby 9.1.12.0 (2.3.3) 2017-06-15 33c6439 Java HotSpot(TM) 64-Bit Server VM 25.92-b14 on 1.8.0_92-b14 +jit [darwin-x86_64]
➜  ~ uname -a
Darwin Olles-MacBook-Pro.local 15.6.0 Darwin Kernel Version 15.6.0: Tue Apr 11 16:00:51 PDT 2017; root:xnu-3248.60.11.5.3~1/RELEASE_X86_64 x86_64

Expected Behavior

2.4.0 :001 > { }.fetch("THE_MOPEDS")
KeyError: key not found: "THE_MOPEDS"
	from (irb):1:in `fetch'
	from (irb):1
	from /Users/olle/.rvm/rubies/ruby-2.4.0/bin/irb:11:in `<main>'

Actual Behavior

jruby-9.1.12.0 :012 > { }.fetch("THE_MOPEDS")
KeyError: key not found: :THE_MOPEDS
	from org/jruby/RubyHash.java:1189:in `fetch'
	from (irb):12:in `<eval>'
	from org/jruby/RubyKernel.java:1000:in `eval'
	from org/jruby/RubyKernel.java:1298:in `loop'
	from org/jruby/RubyKernel.java:1120:in `catch'
	from org/jruby/RubyKernel.java:1120:in `catch'
	from /Users/olle/.rvm/rubies/jruby-9.1.12.0/bin/irb:13:in `<main>'