UnicodeDecodeError Saving votables from astroquery searches

I am encountering UnicodeDecodeErrors while attempting to write astroquery results to votables. An example query which fails upon trying to save to votable format is:

from astroquery.alma import Alma
import astropy.units as u
res = Alma.query_object('PKS1830-211', 1 * u.arcmin)
res.write('PKS1830-211.xml', format='votable')

The resulting error is:

---------------------------------------------------------------------------
UnicodeDecodeError                        Traceback (most recent call last)
<ipython-input-7-1afec7db28b5> in <module>()
----> 1 res.write('PKS1830-211.xml', format='votable')

/usr/lib/python3.6/site-packages/astropy/table/table.py in write(self, *args, **kwargs)
   2548         passed through to the underlying data reader (e.g. `~astropy.io.ascii.write`).
   2549         """
-> 2550         io_registry.write(self, *args, **kwargs)
   2551
   2552     def copy(self, copy_data=True):

/usr/lib/python3.6/site-packages/astropy/io/registry.py in write(data, *args, **kwargs)
    579
    580     writer = get_writer(format, data.__class__)
--> 581     writer(data, *args, **kwargs)
    582
    583

/usr/lib/python3.6/site-packages/astropy/io/votable/connect.py in write_table_votable(input, output, table_id, overwrite, tabledata_format)
    160
    161     # Write out file
--> 162     table_file.to_xml(output, tabledata_format=tabledata_format)
    163
    164

/usr/lib/python3.6/site-packages/astropy/io/votable/tree.py in to_xml(self, fd, compressed, tabledata_format, _debug_python_based_parser, _astropy_version)
   3484                 for element_set in element_sets:
   3485                     for element in element_set:
-> 3486                         element.to_xml(w, **kwargs)
   3487
   3488     def iter_tables(self):

/usr/lib/python3.6/site-packages/astropy/io/votable/tree.py in to_xml(self, w, **kwargs)
   3176                                 self.resources):
   3177                 for element in element_set:
-> 3178                     element.to_xml(w, **kwargs)
   3179
   3180     def iter_tables(self):

/usr/lib/python3.6/site-packages/astropy/io/votable/tree.py in to_xml(self, w, **kwargs)
   2753                 with w.tag('DATA'):
   2754                     if format == 'tabledata':
-> 2755                         self._write_tabledata(w, **kwargs)
   2756                     elif format == 'binary':
   2757                         self._write_binary(1, w, **kwargs)

/usr/lib/python3.6/site-packages/astropy/io/votable/tree.py in _write_tabledata(self, w, **kwargs)
   2778                 tablewriter.write_tabledata(
   2779                     w.write, array.data, array.mask, fields,
-> 2780                     supports_empty_values, indent, 1 << 8)
   2781             else:
   2782                 write = w.write

/usr/lib/python3.6/site-packages/astropy/io/votable/converters.py in output(self, value, mask)
    354             return ''
    355         if not isinstance(value, str):
--> 356             value = value.decode('ascii')
    357         return xml_escape_cdata(value)
    358

UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 211: ordinal not in range(128)

A temporary workaround for me has been to exit votable/converters.py to all decode to utf-8 instead of ascii, but I am not sure this is a robust fix. I saw there were some other issues relating to UnicodeDecodeErrors, but not seemed to specifically address this. But if I’ve missed a known fix or workaround, please let me know.

My software versions are:

• python: 3.6.3
• astropy: 2.0.2
• numpy: 1.13.3

[privong]

@pllim I think the bug is inside astropy, not astoquery? astroquery.alma.Alma.query_object() returns an astropy Table object (https://astroquery.readthedocs.io/en/latest/api/astroquery.alma.AlmaClass.html#astroquery.alma.AlmaClass.query_object and http://docs.astropy.org/en/latest/api/astropy.table.Table.html#astropy.table.Table). So the write() function is in astropy.

[bsipocz]

@pllim - can you open an issue for that (or a fix)?