java.lang.IllegalStateException: Should not acquire Children.MUTEX while holding ProjectManager.mutex()
        at org.openide.nodes.Children$ProjectManagerDeadlockDetector.execute(Children.java:1805)
        at org.openide.util.Mutex.postRequest(Mutex.java:1245)
        at org.openide.util.Mutex.postRequest(Mutex.java:1209)
        at org.openide.util.Mutex.postWriteRequest(Mutex.java:582)
        at org.openide.nodes.Children$Keys.applyKeys(Children.java:1511)
        at org.openide.nodes.Children$Keys.setKeys(Children.java:1455)
        at org.netbeans.modules.python.project.ui.PackageViewChildren.refreshKeys(PackageViewChildren.java:248)
        at org.netbeans.modules.python.project.ui.PackageViewChildren.fileFolderCreated(PackageViewChildren.java:400)
Caused: java.lang.reflect.InvocationTargetException
        at sun.reflect.GeneratedMethodAccessor55.invoke(GeneratedMethodAccessor55.java:0)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.openide.util.WeakListenerImpl$ProxyListener.invoke(WeakListenerImpl.java:450)
Caused: java.lang.reflect.UndeclaredThrowableException
        at $Proxy1.fileFolderCreated(.java:0)
        at org.openide.filesystems.FCLSupport$DispatchEventWrapper.dispatchEventImpl(FCLSupport.java:133)
        at org.openide.filesystems.FCLSupport$DispatchEventWrapper.dispatchEvent(FCLSupport.java:122)
        at org.openide.filesystems.FCLSupport.dispatchEvent(FCLSupport.java:99)
        at org.openide.filesystems.FileObject$ED.dispatch(FileObject.java:1052)
        at org.openide.filesystems.EventControl.invokeDispatchers(EventControl.java:203)
        at org.openide.filesystems.EventControl.exitAtomicAction(EventControl.java:177)
        at org.openide.filesystems.EventControl.runAtomicAction(EventControl.java:122)
        at org.openide.filesystems.FileSystem.runAtomicAction(FileSystem.java:509)
        at org.netbeans.spi.project.support.ant.ProjectProperties$PP.write(ProjectProperties.java:227)
        at org.netbeans.spi.project.support.ant.ProjectProperties.write(ProjectProperties.java:133)
        at org.netbeans.spi.project.support.ant.AntProjectHelper.save(AntProjectHelper.java:593)
        at org.netbeans.spi.project.support.ant.AntProjectHelper.access$100(AntProjectHelper.java:100)
        at org.netbeans.spi.project.support.ant.AntProjectHelper$1.save(AntProjectHelper.java:138)
        at org.netbeans.modules.project.ant.AntBasedProjectFactorySingleton.saveProject(AntBasedProjectFactorySingleton.java:338)
        at org.netbeans.api.project.ProjectManager$6.run(ProjectManager.java:644)
        at org.netbeans.api.project.ProjectManager$6.run(ProjectManager.java:633)
        at org.openide.util.Mutex.writeAccess(Mutex.java:433)
        at org.netbeans.api.project.ProjectManager.saveProject(ProjectManager.java:633)
        at org.netbeans.modules.python.project.ui.customizer.PythonProjectProperties.save(PythonProjectProperties.java:203)
        at org.netbeans.modules.python.project.ui.customizer.PythonCustomizerProvider$StoreListener.actionPerformed(PythonCustomizerProvider.java:79)
        at org.netbeans.modules.project.uiapi.CustomizerDialog$OptionListener$2$1.run(CustomizerDialog.java:244)
        at org.openide.util.Mutex.writeAccess(Mutex.java:394)
        at org.netbeans.modules.project.uiapi.CustomizerDialog$OptionListener$2.run(CustomizerDialog.java:240)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:573)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1005)