Confusing error message when a CSV attachment has empty columns

[lognaturel]

When exporting to CSV from e.g. Excel, there can be some extra blank columns produced (, , , , , , ).

The error message in that case is accurate but not very helpful to someone who is trying to get their form to work:

CSV column heading "" cannot be turned into a valid XML element

Could we ignore those empty columns? What currently happens if one of the data lines is longer than the header?

If we can't ignore them, here are some ideas for a more actionable error message:

• The form attachment <attachment name> has empty columns. Please remove them.
• This can happen when exporting from a spreadsheet program, especially if those columns have formatting.

The audience for that error message is a form create / project lead. Typically this kind of issue wouldn't make it to a data collector / respondent.

If we have to keep an error message, this would be a good candidate for removing the "Please contact..." because the error message should be self-service.

See also https://github.com/enketo/enketo-express/issues/250