JRuby and autotest conspire to produce IOError

-J-Djruby.backtrace.style=raw

Thread.java:1409:in `getStackTrace': closed stream (IOError)
	from RubyException.java:139:in `setBacktraceFrames'
	from RaiseException.java:160:in `setException'
	from RaiseException.java:72:in `<init>'
	from Ruby.java:3031:in `newRaiseException'
	from Ruby.java:2975:in `newIOError'
	from OpenFile.java:151:in `checkClosed'
	from RubyIO.java:304:in `getOpenFileChecked'
	from RubyIO.java:353:in `getInStream'
	from IOInputStream.java:65:in `<init>'
	from Ruby.java:2194:in `getInputStream'
	from ShellLauncher.java:234:in `runAndWait'
	from RubyKernel.java:1287:in `backquote'
	from org/jruby/RubyKernel$s_method_1_0$RUBYINVOKER$backquote.gen:-1:in `call'
	from RubyClass.java:570:in `finvoke'
	from RuntimeHelpers.java:409:in `invoke'
	from RubyBasicObject.java:315:in `callMethod'
	from DXStrNode.java:74:in `interpret'
	from LocalAsgnNode.java:123:in `interpret'
	from NewlineNode.java:104:in `interpret'
	from BlockNode.java:71:in `interpret'
	from InterpretedBlock.java:317:in `evalBlockBody'
	from InterpretedBlock.java:268:in `yield'
	from Block.java:194:in `yield'
	from RubyTempfile.java:221:in `open'
	from org/jruby/RubyTempfile$s_method_0_1$RUBYFRAMEDINVOKER$open.gen:-1:in `call'
	from DynamicMethod.java:168:in `call'
	from CachingCallSite.java:288:in `cacheAndCall'
	from CachingCallSite.java:126:in `callBlock'
	from CachingCallSite.java:131:in `call'
	from CallOneArgBlockNode.java:60:in `interpret'
	from NewlineNode.java:104:in `interpret'
	from BlockNode.java:71:in `interpret'
	from InterpretedBlock.java:317:in `evalBlockBody'
	from InterpretedBlock.java:268:in `yield'
	from Block.java:194:in `yield'
	from RubyTempfile.java:221:in `open'
	from org/jruby/RubyTempfile$s_method_0_1$RUBYFRAMEDINVOKER$open.gen:-1:in `call'
	from DynamicMethod.java:168:in `call'
	from CachingCallSite.java:288:in `cacheAndCall'
	from CachingCallSite.java:126:in `callBlock'
	from CachingCallSite.java:131:in `call'
	from CallOneArgBlockNode.java:60:in `interpret'
	from NewlineNode.java:104:in `interpret'
	from BlockNode.java:71:in `interpret'
	from InterpretedMethod.java:210:in `call'
	from DefaultMethod.java:183:in `call'
	from CachingCallSite.java:298:in `cacheAndCall'
	from CachingCallSite.java:157:in `call'
	from CallTwoArgNode.java:59:in `interpret'
	from CallOneArgNode.java:57:in `interpret'
	from NewlineNode.java:104:in `interpret'
	from BlockNode.java:71:in `interpret'
	from IfNode.java:112:in `interpret'
	from NewlineNode.java:104:in `interpret'
	from BlockNode.java:71:in `interpret'
	from InterpretedBlock.java:317:in `evalBlockBody'
	from InterpretedBlock.java:268:in `yield'
	from Block.java:194:in `yield'
	from RubyArray.java:1562:in `each'
	from org/jruby/RubyArray$i_method_0_0$RUBYFRAMEDINVOKER$each.gen:-1:in `call'
	from CachingCallSite.java:268:in `cacheAndCall'
	from CachingCallSite.java:86:in `callBlock'
	from CachingCallSite.java:91:in `call'
	from CallNoArgBlockNode.java:64:in `interpret'
	from NewlineNode.java:104:in `interpret'
	from BlockNode.java:71:in `interpret'
	from InterpretedMethod.java:136:in `call'
	from DefaultMethod.java:151:in `call'
	from CachingCallSite.java:258:in `cacheAndCall'
	from CachingCallSite.java:77:in `call'
	from CallNoArgNode.java:61:in `interpret'
	from FCallOneArgNode.java:36:in `interpret'
	from NewlineNode.java:104:in `interpret'
	from BlockNode.java:71:in `interpret'
	from InterpretedMethod.java:136:in `call'
	from DefaultMethod.java:151:in `call'
	from CachingCallSite.java:258:in `cacheAndCall'
	from CachingCallSite.java:77:in `call'
	from CallNoArgNode.java:61:in `interpret'
	from NewlineNode.java:104:in `interpret'
	from BlockNode.java:71:in `interpret'
	from RootNode.java:129:in `interpret'
	from Ruby.java:2381:in `loadFile'
	from ExternalScript.java:58:in `load'
	from LoadService.java:253:in `load'
	from RubyKernel.java:914:in `load'
	from org/jruby/RubyKernel$s_method_0_1$RUBYFRAMEDINVOKER$load.gen:-1:in `call'
	from DynamicMethod.java:168:in `call'
	from DynamicMethod.java:164:in `call'
	from CachingCallSite.java:278:in `cacheAndCall'
	from CachingCallSite.java:117:in `call'
	from unit_diff:19:in `__file__'
	from unit_diff:-1:in `load'
	from Ruby.java:592:in `runScript'
	from Ruby.java:514:in `runNormally'
	from Ruby.java:360:in `runFromMain'
	from Main.java:272:in `run'
	from Main.java:117:in `run'
	from Main.java:97:in `main'

no flags

$ jruby -S autotest
/Users/asari/personal/jruby/bin/jruby -X+O -I.:lib:test:../../minitest/dev/lib -rubygems -e "%w[minitest/autorun test/test_zentest.rb test/test_autotest.rb test/test_unit_diff.rb test/test_focus.rb test/test_zentest_mapping.rb].each { |f| require f }" | /Users/asari/personal/jruby/bin/jruby -X+O -s -S unit_diff -u
Loaded suite -e
Started
....................................................................F.................................
Finished in 0.951000 seconds.

/Users/asari/Development/src/jruby/lib/ruby/gems/1.8/gems/ZenTest-4.1.3/lib/unit_diff.rb:231:in `diff': closed stream (IOError)
	from /Users/asari/Development/src/jruby/lib/ruby/gems/1.8/gems/ZenTest-4.1.3/lib/unit_diff.rb:224:in `open'
	from /Users/asari/Development/src/jruby/lib/ruby/gems/1.8/gems/ZenTest-4.1.3/lib/unit_diff.rb:224:in `diff'
	from /Users/asari/Development/src/jruby/lib/ruby/gems/1.8/gems/ZenTest-4.1.3/lib/unit_diff.rb:221:in `open'
	from /Users/asari/Development/src/jruby/lib/ruby/gems/1.8/gems/ZenTest-4.1.3/lib/unit_diff.rb:221:in `diff'
	from /Users/asari/Development/src/jruby/lib/ruby/gems/1.8/gems/ZenTest-4.1.3/lib/unit_diff.rb:201:in `unit_diff'
	from /Users/asari/Development/src/jruby/lib/ruby/gems/1.8/gems/ZenTest-4.1.3/lib/unit_diff.rb:187:in `each'
	from /Users/asari/Development/src/jruby/lib/ruby/gems/1.8/gems/ZenTest-4.1.3/lib/unit_diff.rb:187:in `unit_diff'
	from /Users/asari/Development/src/jruby/lib/ruby/gems/1.8/gems/ZenTest-4.1.3/lib/unit_diff.rb:56:in `unit_diff'
	from /Users/asari/Development/src/jruby/lib/ruby/gems/1.8/gems/ZenTest-4.1.3/bin/unit_diff:37
	from /Users/asari/Development/src/jruby/lib/ruby/gems/1.8/gems/ZenTest-4.1.3/bin/unit_diff:19:in `load'
	from /Users/asari/personal/jruby/bin/unit_diff:19