Caused by: java.lang.ClassCastException: org.gradle.api.plugins.JavaPluginConvention cannot be cast to groovy.lang.GroovyObject
    at org.codehaus.groovy.runtime.callsite.PogoGetPropertySite.getProperty(PogoGetPropertySite.java:50)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGroovyObjectGetProperty(AbstractCallSite.java:307)
    at com.github.jengelman.gradle.plugins.shadow.ShadowJavaPlugin.configureShadowTask(ShadowJavaPlugin.groovy:57)
    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:498)
    at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite$PogoCachedMethodSiteNoUnwrapNoCoerce.invoke(PogoMetaMethodSite.java:210)
    at org.codehaus.groovy.runtime.callsite.PogoMetaMethodSite.callCurrent(PogoMetaMethodSite.java:59)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:52)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:154)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:166)
    at com.github.jengelman.gradle.plugins.shadow.ShadowJavaPlugin.apply(ShadowJavaPlugin.groovy:35)
    at com.github.jengelman.gradle.plugins.shadow.ShadowJavaPlugin.apply(ShadowJavaPlugin.groovy)
    at org.gradle.api.internal.plugins.ImperativeOnlyPluginApplicator.applyImperative(ImperativeOnlyPluginApplicator.java:35)
    at org.gradle.api.internal.plugins.RuleBasedPluginApplicator.applyImperative(RuleBasedPluginApplicator.java:43)
    at org.gradle.api.internal.plugins.DefaultPluginManager.doApply(DefaultPluginManager.java:137)