Pycups

* Fixed build for CUPS 1.6.3 by making several constants conditional
on CUPS >= 1.7.

* Removed private CANCEL_DOCUMENT, GET_DOCUMENT_ATTRIBUTES,
GET_DOCUMENTS, DELETE_DOCUMENT, SET_DOCUMENT_ATTRIBUTES IPP
operation constants.
* Fixed build for CUPS 1.4 by making several constants conditional on
CUPS >= 1.5.

* Fixes for cups.IPP_JOB_CANCELED, cups.IPP_ERROR_JOB_CANCELED,
cups.IPP_STATUS_ERROR_CUPS_AUTHENTICATION_CANCELED,
cups.IPP_AUTHENTICATION_CANCELED,
cups.IPP_STATUS_ERROR_CUPS_UPGRADE_REQUIRED, and
cups.IPP_UPGRADE_REQUIRED.

* cups.ippErrorString(). Fixed build with CUPS 1.5. New-style (CUPS
1.6) naming for HTTP status (cups.HTTP_STATUS_*), IPP orientation
(cups.IPP_ORIENT_*), IPP status (cups.IPP_STATUS_*), and IPP
I/O (cups.IPP_STATE_*) constants.

* cups.IPPRequest.operation, cups.IPPRequest.state,
cups.IPPRequest.statuscode, cups.ippOpString(), cups.IPP_OP_*,
cups.IPPRequest.addSeparator(), cups.IPPRequest.add(),
cups.IPPRequest.writeIO().

* Now builds against CUPS 2.0.
* The rpm provider script is now Python3.