[1.12] Nonsensical ClassDefNotFound Exception

[Vatuu]

So, I've been working on a mod for the last few weeks, and it's finally time to build the actual artefact.

However, while the client launched from the dev-environment works without issues, the actual game downright refuses to start the game with my mod and immediately crashes with the following message:

Spoiler

Caused by: java.lang.NoClassDefFoundError: org/apache/commons/lang/SystemUtils
	at net.arikia.dev.drpc.DiscordRPC.loadDLL(DiscordRPC.java:118)
	at net.arikia.dev.drpc.DiscordRPC.<clinit>(DiscordRPC.java:21)
	at org.minecord.minecord.discord.DiscordUtil.initializeDiscord(DiscordUtil.java:32)
	at org.minecord.minecord.Minecord.preInit(Minecord.java:55)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)
	at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:606)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)
	at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:91)
	at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:150)
	at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:76)
	at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:399)
	at com.google.common.eventbus.Subscriber.dispatchEvent(Subscriber.java:71)
	at com.google.common.eventbus.Dispatcher$PerThreadQueuedDispatcher.dispatch(Dispatcher.java:116)
	at com.google.common.eventbus.EventBus.post(EventBus.java:217)
	at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:253)
	at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:231)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)
	at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:91)
	at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:150)
	at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:76)
	at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:399)
	at com.google.common.eventbus.Subscriber.dispatchEvent(Subscriber.java:71)
	at com.google.common.eventbus.Dispatcher$PerThreadQueuedDispatcher.dispatch(Dispatcher.java:116)
	at com.google.common.eventbus.EventBus.post(EventBus.java:217)
	at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:148)
	at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:602)
	at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:270)
	at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:466)
	at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:377)
	at net.minecraft.client.main.Main.main(SourceFile:123)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)
	at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
	at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang.SystemUtils
	at java.net.URLClassLoader$1.run(URLClassLoader.java:372)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:360)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:106)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	... 45 more

 

The class in question that's throwing the error is a library the mod depends on, made by myself. But here comes the weird part:
Firstly, this error has never occurred in any context other than a forge mod. Secondly, the class in question is definitely existent inside of the build jar.

Spoiler

 

As stated before, the mod launches and runs without an issue inside of the dev environment.

I'd appreciate since this is starting to become rather annoying.

Best regards, Vatuu.

[Vatuu]

Oh, great. Any suggestions?

 

Since apparently, the srgExtra method is not working anymore.

Edited March 8, 2018 by Vatuu

[Vatuu]

I've tried srgExtra "path", reobf{jar{extraLine "path}}, and the addSrgLine("") method, none have worked.