Every time when I start a fresh 8u20-dev build (using jfx+rt+rt-closed repos only), an exception gets thrown. Note that the build continues and completes successfully afterwards. The exception is as follows:

$ JDK_HOME=/d/tools/java/8 gradle
 Defining Closed Properties
:buildSrc:clean UP-TO-DATE
:buildSrc:generateGrammarSourceerror(10): internal error: Can't get property indirectDelegates using method get/isIndirectDelegates from org.antlr.tool.Grammar instance : java.lang.NullPointerException
java.util.Objects.requireNonNull(Objects.java:203)
java.util.ArrayList.removeAll(ArrayList.java:674)
org.antlr.tool.CompositeGrammar.getIndirectDelegates(CompositeGrammar.java:222)
org.antlr.tool.Grammar.getIndirectDelegates(Grammar.java:2620)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:483)
org.antlr.stringtemplate.language.ASTExpr.invokeMethod(ASTExpr.java:563)
org.antlr.stringtemplate.language.ASTExpr.rawGetObjectProperty(ASTExpr.java:514)
org.antlr.stringtemplate.language.ASTExpr.getObjectProperty(ASTExpr.java:416)
org.antlr.stringtemplate.language.ActionEvaluator.attribute(ActionEvaluator.java:351)
org.antlr.stringtemplate.language.ActionEvaluator.expr(ActionEvaluator.java:136)
org.antlr.stringtemplate.language.ActionEvaluator.templateApplication(ActionEvaluator.java:216)
org.antlr.stringtemplate.language.ActionEvaluator.expr(ActionEvaluator.java:126)
org.antlr.stringtemplate.language.ActionEvaluator.action(ActionEvaluator.java:84)
org.antlr.stringtemplate.language.ASTExpr.write(ASTExpr.java:148)
org.antlr.stringtemplate.StringTemplate.write(StringTemplate.java:700)
org.antlr.stringtemplate.language.ASTExpr.write(ASTExpr.java:722)
org.antlr.stringtemplate.language.ASTExpr.writeAttribute(ASTExpr.java:659)
org.antlr.stringtemplate.language.ActionEvaluator.action(ActionEvaluator.java:86)
org.antlr.stringtemplate.language.ASTExpr.write(ASTExpr.java:148)
org.antlr.stringtemplate.StringTemplate.write(StringTemplate.java:700)
org.antlr.stringtemplate.language.ASTExpr.write(ASTExpr.java:722)
org.antlr.stringtemplate.language.ASTExpr.writeAttribute(ASTExpr.java:659)
org.antlr.stringtemplate.language.ActionEvaluator.action(ActionEvaluator.java:86)
org.antlr.stringtemplate.language.ASTExpr.write(ASTExpr.java:148)
org.antlr.stringtemplate.StringTemplate.write(StringTemplate.java:700)
org.antlr.stringtemplate.language.ASTExpr.write(ASTExpr.java:722)
org.antlr.stringtemplate.language.ASTExpr.writeAttribute(ASTExpr.java:659)
org.antlr.stringtemplate.language.ActionEvaluator.action(ActionEvaluator.java:86)
org.antlr.stringtemplate.language.ASTExpr.write(ASTExpr.java:148)
org.antlr.stringtemplate.StringTemplate.write(StringTemplate.java:700)
org.antlr.codegen.CodeGenerator.write(CodeGenerator.java:1278)
org.antlr.codegen.Target.genRecognizerFile(Target.java:94)
org.antlr.codegen.CodeGenerator.genRecognizer(CodeGenerator.java:463)
org.antlr.Tool.generateRecognizer(Tool.java:607)
org.antlr.Tool.process(Tool.java:429)
org.antlr.Tool.main(Tool.java:91)

:buildSrc:compileJava