FAILURE: Build failed with an exception.

$ rm -Rf build ; gradle installShadowDist
[...]
FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':***********:installShadowDist'.
> The specified installation directory '/**********/build/install/********-shadow' is neither empty nor does it contain an installation for '*********'.
  If you really want to install to this directory, delete it and run the install task again.
  Alternatively, choose a different installation directory.

plugins {
	id 'java'
	id 'groovy'
	id 'application'
	id 'com.github.johnrengelman.shadow' version '2.0.1' // variable cannot be used here!
}

repositories {
	jcenter()
	maven {
		url "https://oss.sonatype.org/content/repositories/snapshots"
	}
}

sourceCompatibility = '1.8'

dependencies {
	compile group: 'org.codehaus.groovy', name: 'groovy-all', version: versions.groovy
	compile project('*****INTERNAL DEPENDENCY*******')
	compile project('*****INTERNAL DEPENDENCY*******')
	compile "io.vertx:vertx-core:${versions.vertx}"
	compile "io.vertx:vertx-rx-java:${versions.vertx}"
	compile "io.vertx:vertx-lang-groovy:${versions.vertx}"
	compile "io.vertx:vertx-rx-groovy:${versions.vertx}"
	compile "com.julienviet:childprocess-vertx-ext:${versions.childprocess_vertx_ext}"   // Child Process extension for Vert.x ; see https://github.com/vietj/childprocess-vertx-ext
}

mainClassName = "*******************.Main"
applicationDefaultJvmArgs = ["-Dvertx.cacheDirBase=/tmp/vertx-cache"]	// so that a .vertx/ directory is NOT created in $CWD

shadowJar {
	mergeGroovyExtensionModules()
	classifier = 'fat'
	mergeServiceFiles {
		include 'META-INF/services/io.vertx.core.spi.VerticleFactory'
	}
}