handle errors when not adding a loaded component

src/jflow/workflow.py

@@ -111,28 +111,32 @@ class Workflow(threading.Thread):
     
     def add_component(self, component_name, args=[], kwargs={}, component_prefix="default"):
         # first build and check if this component is OK
-        my_pckge = __import__(self.comp_pckg[component_name], globals(), locals(), [component_name], -1)
-        # build the object and define required field
-        cmpt_object = getattr(my_pckge, component_name)()
-        cmpt_object.output_directory = self.get_component_output_directory(component_name, component_prefix)
-        cmpt_object.prefix = component_prefix
-        if kwargs: cmpt_object.define_parameters(**kwargs)
-        else: cmpt_object.define_parameters(*args)
-        
-        # if already init, add the component to the list and check if weaver should be executed
-        if self.component_nameids_is_init:
-            # add the component
-            self.components.append(cmpt_object)
-            # if this one require a dynamic pipeline, execute the first part
-            if cmpt_object.is_dynamic:
-                self._execute_weaver()
-        else: 
-            if self._component_is_duplicated(cmpt_object):
-                raise ValueError("Component " + cmpt_object.__class__.__name__ + " with prefix " + 
-                                 cmpt_object.prefix + " already exist in this pipeline!")
-            self.component_nameids[cmpt_object.get_nameid()] = None
+        if self.comp_pckg.has_key(component_name):
+            my_pckge = __import__(self.comp_pckg[component_name], globals(), locals(), [component_name], -1)
+            # build the object and define required field
+            cmpt_object = getattr(my_pckge, component_name)()
+            cmpt_object.output_directory = self.get_component_output_directory(component_name, component_prefix)
+            cmpt_object.prefix = component_prefix
+            if kwargs: cmpt_object.define_parameters(**kwargs)
+            else: cmpt_object.define_parameters(*args)
+            
+            # if already init, add the component to the list and check if weaver should be executed
+            if self.component_nameids_is_init:
+                # add the component
+                self.components.append(cmpt_object)
+                # if this one require a dynamic pipeline, execute the first part
+                if cmpt_object.is_dynamic:
+                    self._execute_weaver()
+            else: 
+                if self._component_is_duplicated(cmpt_object):
+                    raise ValueError("Component " + cmpt_object.__class__.__name__ + " with prefix " + 
+                                     cmpt_object.prefix + " already exist in this pipeline!")
+                self.component_nameids[cmpt_object.get_nameid()] = None
+
+            return cmpt_object
         
-        return cmpt_object
+        else:
+            sys.exit(component_name + " component cannot be loaded, available components are: " + ", ".join(self.comp_pckg.keys()))
     
     def pre_process(self):
         pass