[utils] rework '_check_module_for_class'

pypushflow/addon/utils.py

@@ -62,19 +62,19 @@ def _check_module_for_class(module, depth=0):
         if inspect.ismodule(m[1]):
             if inspect.isclass(m[1]):
                 classes.append(m[1])
-
-            for importer, modname, ispkg in pkgutil.iter_modules(
-                    m[1].__path__):
-                module_name = module.__name__
-                submod_name = '.'.join((module_name, m[0], modname))
-                try:
-                    mod = importlib.import_module(submod_name)
-                except Exception:
-                    pass
-                else:
-                    classes.extend(
-                        _check_module_for_class(module=mod,
-                                                depth=depth+1))
+            elif hasattr(m[1], '__path__'):
+                for importer, modname, ispkg in pkgutil.iter_modules(
+                        m[1].__path__):
+                    module_name = module.__name__
+                    submod_name = '.'.join((module_name, m[0], modname))
+                    try:
+                        mod = importlib.import_module(submod_name)
+                    except Exception:
+                        pass
+                    else:
+                        classes.extend(
+                            _check_module_for_class(module=mod,
+                                                    depth=depth+1))
     return classes