Address suggestions from code review

Co-authored-by: Carlotta Sartore <[email protected]>

src/rod/__main__.py

@@ -59,15 +59,17 @@ def main() -> None:
 
     args = parser.parse_args()
 
-    log_level = "DEBUG" if args.verbose else "INFO"
+    log_level = logging.DEBUG if args.verbose else logging.INFO
 
     logging.basicConfig(level=log_level)
 
     from rod.urdf.exporter import UrdfExporter
 
     # Ensure file argument is provided if output or `show` is specified.
     if not args.file and (args.output or args.show):
-        parser.error("The following arguments are required: FILE.")
+        parser.error(
+            "The `--file` argument is required when using `--output` or `--show`."
+        )
 
     # Show the file attributes if no output file is specified.
     if args.file and not (args.output or args.show):