Every set of messages returned from a command sent through the API will
include exactly one failure message or exactly one success message, and
an arbitrary number of warnings. As a simple alternative to full XML 
support of these return codes, it is possible to simply search for a 
failure result or a success result, and use that to report the status, 
ignoring all text and warnings.

Failure codes:
Error 500 is a free format error message coming out of the OS or other software.

500, %exception-msg%
501, invalid command '%form(command)'
502, required parameter 'type' is missing
502, required parameter 'user' is missing
502, required parameter 'zone' is missing
503, you are not entitled to delete this user
503, you are not entitled to modify this user
503, you are not entitled to route for this user
504, expiration time must be greater than 1/1/1972
505, you are not entitled to modify this zone
506, this user already has a trial zone
507, these nameservers are not compatible
508, nameserver '%form(ns1)' is invalid
508, nameserver '%form(ns2)' is invalid
508, nameserver '%form(ns3)' is invalid
508, nameserver '%form(ns4)' is invalid
510, failure followed by success %num% (This error should never occur)
511, failure followed by warning %num% (This error should never occur)

Warnings:
301, user already exists
301, user is not in the database
302, zone '%form(zone)' already exists for user '%form(user)'

Success Codes:
200, user successfully added
200, zone successfully added
200, user '%form(user)' was deleted
200, zone '%form(zone)' was deleted for user '%form(user)'
201, user not changed
201, zone not added or modified
201, user not deleted
201, user's zone was not deleted
202, user successfully updated