Return the error message text associated with a batch server
Because different server implementations may have different error conditions,
the batch request - reply protocol allows for the server to include the
text of an error message in the reply to a batch request.
If the preceding batch interface library call over the connection specified by
resulted in an error return from the server,
there may be an associated text message. If it exists, this function
will return a pointer to the null terminated text string.