A syntax-corrected version of the code in https://stackoverflow.com/a/46594963/39791

saveDataFrameAsCSV.scala

/**
 *
 * Write a dataframe to CSV at the location specified. Assumes that the contents
 * of the dataframe being written are small enough to fit in memory on the Spark
 * master. (I use this for deequ suggested checks, which is usually less than 30
 * or so entries.)
 *
 */
import org.apache.spark.sql._

import org.apache.hadoop.fs.{FileSystem, Path}
import org.apache.hadoop.conf.Configuration

import java.io.{BufferedWriter, OutputStreamWriter}

val SPARK_WRITE_LOCATION = "/tmp"

def saveCSV(spark: SparkSession, results : DataFrame, filename: String) {
    var fs = FileSystem.get(spark.sparkContext.hadoopConfiguration)

    if (spark.conf.get("spark.master").toString.contains("local")) {
      fs = FileSystem.getLocal(new Configuration())
    }

    val tempWritePath = new Path(SPARK_WRITE_LOCATION)
    if (fs.exists(tempWritePath)) {
      val x = fs.delete(new Path(SPARK_WRITE_LOCATION), true)
      assert(x)
    }

    if (results.count > 0) {
      val hadoopFilepath = new Path(SPARK_WRITE_LOCATION, filename)
      val writeStream = fs.create(hadoopFilepath, true)
      val bw = new BufferedWriter( new OutputStreamWriter( writeStream, "UTF-8" ) )

      val x = results.collect()
      for (row : Row <- x) {
        val rowString = row.mkString(start = "", sep = ",", end="\n")
        bw.write(rowString)
      }

      bw.close()
      writeStream.close()

      val resultsWritePath = new Path(SPARK_WRITE_LOCATION, filename)

      if (fs.exists(resultsWritePath)) {
        fs.delete(resultsWritePath, true)
      }
      fs.copyToLocalFile(false, hadoopFilepath, resultsWritePath, true)
    }
  }