Fixed #1769 Suggest to rename the image name

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

@@ -46,6 +46,16 @@
     void process(ImageConfiguration imageConfiguration) throws JKubeServiceException;
   }
 
+  protected String getHintFromException(Exception ex) {
+    String message = "Error while trying to push the image: " + ex.getMessage();
+    if(ex.getMessage().contains("denied") || ex.getMessage().contains("unauthorized")) {
+      message += "\nPossible issues: invalid credentials or incorrect image name or registry." +
+                 "\nHint: Check your credentials." +
+                 "\nHint: Image name can be modified with the jkube.generator.name property";
+    }
+    return message;
+  }
+
   private void processImage(ImageConfigurationProcessor imageConfigurationConsumer, String skipMessage, ImageConfiguration... imageConfigurations) throws JKubeServiceException {
     if (imageConfigurations != null) {
       for (ImageConfiguration imageConfiguration : imageConfigurations) {

jkube-kit/config/service/src/main/java/org/eclipse/jkube/kit/config/service/kubernetes/DockerBuildService.java

@@ -70,7 +70,7 @@
         try {
             dockerServices.getRegistryService().pushImage(imageConfiguration, retries, registryConfig, skipTag);
         } catch (IOException ex) {
-            throw new JKubeServiceException("Error while trying to push the image: " + ex.getMessage(), ex);
+            throw new JKubeServiceException(getHintFromException(ex), ex);
         }
     }
 

jkube-kit/config/service/src/main/java/org/eclipse/jkube/kit/config/service/kubernetes/JibBuildService.java

@@ -116,7 +116,7 @@
                 log
             );
         } catch (Exception ex) {
-            throw new JKubeServiceException("Error when push JIB image", ex);
+            throw new JKubeServiceException(getHintFromException(ex), ex);
         }
     }