API Troubleshooting for a_v4_extfn

The describe_column, describe_parameter, and describe_udf v4 API methods can return generic error messages. Executing a UDF that does not exist on the server returns a Could not execute statement error.

• Generic describe_column Errors
  Common error returns for describe_column get and set calls.
• Generic describe_udf Errors
  Common error returns for describe_udf get and set calls.
• Generic describe_parameter Errors
  Common error returns for describe_parameter get and set calls.
• Missing UDF Returns an Error
  An attempt to execute a UDF that does not exist on the server returns an error.