TestAllFiles: Add output if a file cannot be matched to a handler
diff --git a/poi-integration/src/test/java/org/apache/poi/stress/TestAllFiles.java b/poi-integration/src/test/java/org/apache/poi/stress/TestAllFiles.java
index 8988c8a..b73914f 100644
--- a/poi-integration/src/test/java/org/apache/poi/stress/TestAllFiles.java
+++ b/poi-integration/src/test/java/org/apache/poi/stress/TestAllFiles.java
@@ -172,6 +172,7 @@
                 continue;
             }
 
+            boolean found = false;
             for (FileHandlerKnown handler : sm.getHandler(file)) {
                 ExcInfo info1 = sm.getExcInfo(file, testName, handler);
                 if (info1 == null || info1.isValid(testName, handler.name())) {
@@ -182,8 +183,13 @@
                         (info1 != null) ? info1.getExClazz() : null,
                         (info1 != null) ? info1.getExMessage() : null
                     ));
+                    found = true;
                 }
             }
+
+            if (!found) {
+                System.out.println("Could not find a handler for " + file);
+            }
         }
 
         return result.stream();