Translation Invalid (Signs)

Maybe intended.

I guess you can see that by the name invalid. It is apprently a test translation to test wether or not Minecraft handles invalid translations correctly.

Error message

[18:22:58] [Client thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: fc: Error parsing: TranslatableComponent{key='translation.test.invalid', args=[], siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}: Unsupported format: '%'
	at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_25]
	at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_25]
	at g.a(SourceFile:61) [1.8.7.jar:?]
	at ave.av(SourceFile:880) [1.8.7.jar:?]
	at ave.a(SourceFile:325) [1.8.7.jar:?]
	at net.minecraft.client.main.Main.main(SourceFile:124) [1.8.7.jar:?]
Caused by: fc: Error parsing: TranslatableComponent{key='translation.test.invalid', args=[], siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}: Unsupported format: '%'
	at fb.b(SourceFile:96) ~[1.8.7.jar:?]
	at fb.g(SourceFile:51) ~[1.8.7.jar:?]
	at fb.iterator(SourceFile:152) ~[1.8.7.jar:?]
	at com.google.common.collect.Lists.newArrayList(Lists.java:129) ~[guava-17.0.jar:?]
	at avu.a(SourceFile:25) ~[1.8.7.jar:?]
	at avt.a(SourceFile:139) ~[1.8.7.jar:?]
	at avt.a(SourceFile:129) ~[1.8.7.jar:?]
	at avt.a(SourceFile:125) ~[1.8.7.jar:?]
	at bcy.a(SourceFile:527) ~[1.8.7.jar:?]
	at fy.a(SourceFile:44) ~[1.8.7.jar:?]
	at fy.a(SourceFile:9) ~[1.8.7.jar:?]
	at fh$1.run(SourceFile:13) ~[1.8.7.jar:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_25]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_25]
	at g.a(SourceFile:60) ~[1.8.7.jar:?]
	... 3 more

However like in many cases catching the error would definitely make more sense.

translation.test.invalid is in fact a test string for causing that exceptions.