SPARK-26108 <https://issues.apache.org/jira/browse/SPARK-26108> / PR#23080 <https://github.com/apache/spark/pull/23080> added a require on CSVOptions#lineSeparator to be a single character.
AFAICT, this keeps us from writing CSV files with \r\n line terminators. Wondering if this was intended or a bug? Is there an alternative mechanism or something else I'm missing?
