less warnings for non-empty directories during purge

src/main/java/com/inteligr8/maven/ban/PurgeRepoMojo.java

@@ -16,6 +16,7 @@ package com.inteligr8.maven.ban;
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.DirectoryNotEmptyException;
 import java.nio.file.FileVisitResult;
 import java.nio.file.FileVisitor;
 import java.nio.file.Files;
@@ -328,6 +329,8 @@ public class PurgeRepoMojo extends AbstractMojo {
         public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
             try {
                 Files.delete(dir);
+            } catch (DirectoryNotEmptyException dnee) {
+                getLog().debug("The folder will not be deleted as it is not empty: " + dir);
             } catch (IOException ie) {
                 getLog().debug(ie);
                 getLog().warn("The folder failed to delete: " + dir);