DataType.fromJson should throw an exception with better message

scala> import org.apache.spark.sql.types.DataType
import org.apache.spark.sql.types.DataType

scala> DataType.fromJson( """"abcd"""")
java.util.NoSuchElementException: key not found: abcd
  at scala.collection.MapLike$class.default(MapLike.scala:228)
  at scala.collection.AbstractMap.default(Map.scala:59)
  at scala.collection.MapLike$class.apply(MapLike.scala:141)
  at scala.collection.AbstractMap.apply(Map.scala:59)
  at org.apache.spark.sql.types.DataType$.nameToType(DataType.scala:118)
  at org.apache.spark.sql.types.DataType$.parseDataType(DataType.scala:132)
  at org.apache.spark.sql.types.DataType$.fromJson(DataType.scala:104)
  ... 48 elided

scala> DataType.fromJson( """{"abcd":"a"}""")
scala.MatchError: JObject(List((abcd,JString(a)))) (of class org.json4s.JsonAST$JObject)
  at org.apache.spark.sql.types.DataType$.parseDataType(DataType.scala:130)
  at org.apache.spark.sql.types.DataType$.fromJson(DataType.scala:104)
  ... 48 elided

scala> DataType.fromJson( """{"fields": [{"a":123}], "type": "struct"}""")
scala.MatchError: JObject(List((a,JInt(123)))) (of class org.json4s.JsonAST$JObject)
  at org.apache.spark.sql.types.DataType$.org$apache$spark$sql$types$DataType$$parseStructField(DataType.scala:169)
  at org.apache.spark.sql.types.DataType$$anonfun$parseDataType$1.apply(DataType.scala:150)
  at org.apache.spark.sql.types.DataType$$anonfun$parseDataType$1.apply(DataType.scala:150)
  at scala.collection.immutable.List.map(List.scala:273)
  at org.apache.spark.sql.types.DataType$.parseDataType(DataType.scala:150)
  at org.apache.spark.sql.types.DataType$.fromJson(DataType.scala:104)
  ... 48 elided