Declare errorDetected signal on CLI directory watcher

Libs/CommandLineModules/Core/ctkCmdLineModuleDirectoryWatcher.h

@@ -72,7 +72,7 @@ public:
 
   /**
    * \brief Set the watcher into debug mode, for more output.
-   * \param debug if true, you get more output, otherwise, less output.
+   * \param debug if true, you get more output on the console, otherwise, less output.
    */
   void setDebug(bool debug);
 
@@ -107,6 +107,13 @@ public:
    */
   QStringList commandLineModules() const;
 
+Q_SIGNALS:
+
+  /**
+   * \brief Signals that an error was detected, and the caller should raise an error to the user.
+   */
+  void errorDetected(const QString&);
+
 private:
 
   QScopedPointer<ctkCmdLineModuleDirectoryWatcherPrivate> d;