Clearify error message if user tries to uninstall a nonkube site.

Author: lynnemorrison

internal/cmd/skupper/system/nonkube/system_uninstall.go

@@ -99,7 +99,7 @@ func (cmd *CmdSystemUninstall) Run() error {
 	err := cmd.SystemUninstall(string(config.GetPlatform()))
 
 	if err != nil {
-		return fmt.Errorf("failed to uninstall : %s", err)
+		return fmt.Errorf("Unable to communicate with the Container Engine.\nRun: \"skupper system install\" to prepare the local environment and start the controller.\n\nError: %s", err)
 	}
 
 	return nil

internal/cmd/skupper/system/nonkube/system_uninstall_test.go

@@ -139,7 +139,7 @@ func TestCmdSystemUninstall_Run(t *testing.T) {
 		{
 			name:               "disable socket fails",
 			disableSocketFails: true,
-			errorMessage:       "failed to uninstall : disable socket fails",
+			errorMessage:       "Unable to communicate with the Container Engine.\nRun: \"skupper system install\" to prepare the local environment and start the controller.\n\nError: disable socket fails",
 			flags:              &common.CommandSystemUninstallFlags{Force: false},
 		},
 	}