Merge pull request !6 from WeidenthalerMatthias/fix.header_tofile

csst_fs/fits/fsspec_header.py

@@ -4,7 +4,7 @@ from ..fsspec_fileobj import open_fileobj
 from ..s3_config import load_s3_options
 
 def tofile(fits_header, out_path, s3_options=load_s3_options(), *args, **kwargs):
-    fileobj = open_fileobj(out_path, s3_options)
+    fileobj = open_fileobj(out_path, s3_options, mode='wb')
     fits_header.tofile(fileobj, *args, **kwargs)
     if hasattr(fileobj, 'close'):
         fileobj.close()