ezeep/pyipptool — pull request #44 by sbellem (2013-12-11 15:37:08+00:00)
Title: Changed default argument value for printer_uri to colander.null

As stated in [RFC 2911, section 3.3.4](http://tools.ietf.org/search/rfc2911#section-3.3.4):

> 3.3.4.1 Get-Job-Attributes Request
>
> The following groups of attributes are part of the Get-Job-Attributes
> Request when the request is directed at a Job object:
>
> Group 1: Operation Attributes
>
> Target:
> Either (1) the "printer-uri" (uri) plus "job-id"
> (integer(1:MAX)) or (2) the "job-uri" (uri) operation
> attribute(s) which define the target for this operation as
> described in section 3.1.5.

one may pass either the `job-uri` **OR** (`printer-uri` **AND** `job-id`), in order to fetch the job attributes ... so we're allowing a `colander.null` value for the `printer_uri`, which makes it optional, and when not received, will not be included in the request.