The validate_columns function was developed in response to Code for San Jose's CSV-Validator project. The issue was that files to be uploaded should be verified as valid for CKAN. The function is passed a string argument which is the path/filename to the file to validate as CKAN ready. It raises CkanError exceptions: DuplicateColumnError in the event that one or more column name is duplicated, ColumnMismatchError in the event that not all rows in the file have the same number of columns, and NoDataError if the file contains only a single column or row.