added option to redirect log into a specified file

parsedmarc/cli.py

@@ -223,6 +223,8 @@ def _main():
                             help="only print errors and warnings")
     arg_parser.add_argument("--debug", action="store_true",
                             help="print debugging information")
+    arg_parser.add_argument("--log-file", default=None,
+                            help="redirect logging to file")
     arg_parser.add_argument("-v", "--version", action="version",
                             version=__version__)
 
@@ -237,6 +239,11 @@ def _main():
     if args.debug:
         logging.basicConfig(level=logging.DEBUG)
         logger.setLevel(logging.DEBUG)
+    if args.log_file:
+        fh = logging.FileHandler(args.log_file)
+        formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
+        fh.setFormatter(formatter)
+        logger.addHandler(fh)
     if args.host is None and len(args.file_path) == 0:
         arg_parser.print_help()
         exit(1)