Tools: ignore missing, empty or 'none' experiment type

expconfig.py

@@ -439,7 +439,8 @@ class ExpConfig(ConfigObj):
         else:
             pre_config = user_config
 
-        experiment_type = extra_dict.get('EXP_TYPE', pre_config['EXP_TYPE'])
+        experiment_type = extra_dict.get('EXP_TYPE',
+            pre_config.get('EXP_TYPE', ''))
         # Empty environment should load default
         environment = extra_dict.get('ENVIRONMENT', 
                       pre_config.get('ENVIRONMENT',
@@ -517,7 +518,7 @@ class ExpConfig(ConfigObj):
             split_shared_sections(pre_config)
             list_assign(pre_config)
             register_version(pre_config, config_versions)
-        else:
+        elif experiment_type and experiment_type.lower() != 'none':
             feedback.warning("cannot find experiment config for '%s', "+
                              "using default only", experiment_type)