Prule: Add stdout.flush

prule/__main__.py

@@ -519,6 +519,7 @@ if __name__ == "__main__":
             try:
                 json.dump(job_output, sys.stdout)
                 print() # add newline after json
+                sys.stdout.flush()
             except Exception as e:
                 error_msg = "Error on writing to stdout"
                 log.print(log.error, error_msg)