Meta-ticket for Python 3.3+ preparation (sage library) - stage 2

[wluebbe]

This meta-ticket tracks those tickets for changing the Sage library that did not go into stage 1 (ticket:15980).

Some reasons for assigning tasks to stage 2:

• The code can run on Python 2 only with the support of imported "compatibility" libraries. [copied from description] Maybe we have to check the licenses of the used compatibility libraries.
• The tasks are usually more complicated. The approach may not be obvious or uncontroversial.
• To make progress we need a Python 3.3 test environment for them.

This ticket is referenced by the meta-ticket ticket:15530

No.	2to3 fixer	see ticket	Comment
2	basestring	ticket:16064	about 27 modules; details see ticket
7	exec	ticket:16065	6 modules; details see ticket
8	execfile	ticket:16066	2 modules; details see ticket
10	filter	ticket:16067	about 53 modules; details see ticket (from future_builtins import filter ?)
17	imports	ticket:16069	about 39 modules; details see ticket
22	itertools_import	ticket:16070	about 12 modules; details see ticket
23	itertools	ticket:16071	about 20 modules; details see ticket
24	long	ticket:16072	about 72 modules; details see ticket
25	map	ticket:16073	about 171 modules; details see ticket (from future_builtins import map ?)
26	metaclass	ticket:16074	about 30 modules; details see ticket
29	next	ticket:16075	about 84 modules; details see ticket
30	nonzero	ticket:16076	about 25 modules; details see ticket
36	raw_input	ticket:16077	3 modules; details see ticket
37	reduce	ticket:16078	about 24 modules; details see ticket
46	unicode	ticket:16079	lots of modules?; details see ticket (from __future__ import unicode_literals ?)
47	urllib	ticket:16080	about 16 modules; details see ticket
49	xrange	ticket:16081	about 293 modules changes; details see ticket
51	zip	ticket:16082	about 54 modules; details see ticket (from future_builtins import zip ?)