Confusing error when no credentials set up

Not quite sure where it comes from, since it does not look like a typical S3 error:

copy (select s from generate_series(1,10) s) to 's3://mybucket/tmp/pg.parquet';
ERROR:  failed to close parquet writer: External: Generic S3 error: Client error with status 404 Not Found: <?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
                 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
 <head>
  <title>404 - Not Found</title>
 </head>
 <body>
  <h1>404 - Not Found</h1>
 </body>
</html>

CrunchyData / pg_parquet

Confusing error when no credentials set up #71