E:\Development\Forge Modding\Development>gradlew setupDecompWorkspace
Download http://files.minecraftforge.net/maven/net/minecraftforge/gradle/ForgeGr
adle/2.1-SNAPSHOT/ForgeGradle-2.1-20160302.010421-27.jar
Download https://jcenter.bintray.com/com/github/abrarsyed/jastyle/jAstyle/1.3/jA
style-1.3.jar

FAILURE: Build failed with an exception.

* Where:
Build file 'E:\Development\Forge Modding\Development\build.gradle' line: 36

* What went wrong:
A problem occurred evaluating root project 'Development'.
> This mapping 'stable_20' exists only for MC 1.8.8!

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug
option to get more log output.

BUILD FAILED

Total time: 17 mins 12.403 secs

E:\Development\Forge Modding\Development>