Move argument parsing into a function

mailman_sync.py

@@ -103,7 +103,8 @@ def main(mailman_bin: Path, api: str, api_auth: str, list_suffix: str, dry_run:
             print(f"Skipping {list_name}, as it does not exist in Mailman")
 
 
-if __name__ == "__main__":
+
+def parse_arguments():
     argp = argparse.ArgumentParser(description=__doc__)
     argp.add_argument(
         "--bin",
@@ -119,7 +120,11 @@ if __name__ == "__main__":
         action="store_true",
         help="Don't make changes, just print what would happen",
     )
-    args = argp.parse_args()
+    return argp.parse_args()
+
+
+if __name__ == "__main__":
+    args = parse_arguments()
 
     if "API_AUTH" in os.environ:
         api_auth = os.environ.get("API_AUTH")