Added missing self

pet-wrapper-api.py

@@ -435,7 +435,7 @@ class PET(plugin.PluginAbstract):
         if "alti_file" not in config_dict or not config_dict["alti_file"]:
             logger.error("Can't find altitude file")
 
-        config_dict["windname"] = "".join(element for element in project_vars[config_dict["project"]] if "sfc" in element)
+        config_dict["windname"] = "".join(element for element in self.project_vars[config_dict["project"]] if "sfc" in element)
 
         self.check_variables(config_dict)
         self.extract_timeperiod(config_dict)