Bug fix: the server thread crashed when a callback tango attribute was not...

Bug fix: the server thread crashed when a callback tango attribute was not running, added a ping() that can be catched

src/DonkiDirectorServer.py

@@ -66,11 +66,13 @@ class DonkiDirectorServer (PyTango.LatestDeviceImpl):
             try:
                 if attr not in self.file_finished_proxies.keys():
                     self.file_finished_proxies[attr] = PyTango.AttributeProxy(attr)
+                (self.file_finished_proxies[attr]).ping()
                 (self.file_finished_proxies[attr]).write(filename_in)
             except:
-                self.error_stream("Unable to set callback attribute: " + attr )
+                _errmsg = "ERROR writing callback attribute: " + attr
+                self.error_stream(_errmsg )
+                self.dt._report_message(_errmsg, with_date=True)
                 self.error_stream(traceback.format_exc())
-                
             
     #----- PROTECTED REGION END -----#	//	DonkiDirectorServer.global_variables