I have been bothered recently by a flashing error icon accompanied by the
strange stack trace

WARNING [global]
java.io.IOException: Owner timed out
	at sun.awt.X11.XSelection.getData(XSelection.java:348)
	at sun.awt.X11.XClipboard.getClipboardData(XClipboard.java:98)
	at
sun.awt.datatransfer.ClipboardTransferable.fetchOneFlavor(ClipboardTransferable.java:101)
	at sun.awt.datatransfer.ClipboardTransferable.<init>(ClipboardTransferable.java:80)
	at sun.awt.X11.XClipboard.getContents(XClipboard.java:84)
	at org.netbeans.core.NbClipboard.run(NbClipboard.java:218)
	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:519)
[catch] at
org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:951)

This is strange because none of those lines of code catch and print an
IOException. Finally I figured out that retrieving javaFileListFlavor throws
this exception sometimes and tracked it down to
DataFolder.FolderNode.getDraggedFilesList, which catches IOException and used to
read

ErrorManager.getDefault().notify( ErrorManager.INFORMATIONAL, ex );

but now reads

Logger.global.log(Level.WARNING, null, ex);

The former code definitely never showed the flashing error icon. It only printed
a stack trace. Apparently the new code does show the flashing error icon, which
is a regression. Please fix the rule, and consider reviewing that code you have
already changed by this rule. Or perhaps the default level required to show the
flashing icon needs to be changed, I am not sure.

(In this case I in fact plan to suppress the exception altogether, since it is
annoying and useless, but that is a different matter.)