This packet is sent by the server when an error has occurred.
It contains a list of ErrorField objects, which have the following properties:
fieldType (byte): the type of error -- see the Vertica documentation for the meaning of this code
fieldValue (string): the value for the error field
errorFields (List<ErrorField>): the error fields
getErrorString(): returns a string containing all the error fields in this packet
addErrorField(byte fieldType, string fieldValue): adds a new ErrorField to this packet