Refactor and Rename handleNoImageFoundException for Clarity

- Updated findTagSha to handle String return from handleNoImageFoundException
- Renamed handleNoImageFoundException to generateImageStreamErrorMessage for more accurate and descriptive name

jkube-kit/config/service/src/main/java/org/eclipse/jkube/kit/config/service/openshift/ImageStreamService.java

@@ -194,7 +194,7 @@ private String findTagSha(OpenShiftClient client, String imageStreamName, String
             }
         }
         // Handle the case when no image is found after all retries:
-        throw handleNoImageFoundException(currentImageStream, imageStreamName);
+        return generateImageStreamErrorMessage(currentImageStream, imageStreamName);
     }
 
     // Method to sleep the current thread for a given amount of time
@@ -242,11 +242,11 @@ private TagEvent updateLatestTagFromList(TagEvent latestTag, NamedTagEventList l
     }
 
     // Method to handle cases where no image is found
-    private IllegalStateException handleNoImageFoundException(ImageStream currentImageStream, String imageStreamName) {
+    private String generateImageStreamErrorMessage(ImageStream currentImageStream, String imageStreamName) {
         if (currentImageStream == null) {
-            return new IllegalStateException("Could not find ImageStream with name " + imageStreamName + "in namespace " + namespace);
+            return "Could not find ImageStream with name " + imageStreamName + " in namespace " + namespace;
         } else {
-            return new IllegalStateException("Could not find a tag in the ImageStream " + imageStreamName);
+            return "Could not find a tag in the ImageStream " + imageStreamName;
         }
     }