[pylint] Fix W0621 - Redefining buil-in 'id'. Change to ids.
[pylint] Fix W0102 - Dangerous default value {} as argument. Change to
default=None and add a 'default = default or {}' line.
[pylint] Fix C0325 - Unnecessary parens after u'not' keyword. Remove
parens.
[pylint] Fix W0622 - Redefining built-in 'sum'. Change to sum_vat
[pylint] Fix W0702 - No exception type(s) specified. Change to except Exception, e.
[pylint] C0103 - Invalid variable name "s". Change to url_obj.
[pylint] C0103 - Invalid variable name "r". Change to url_str.
[pylint] Fix W0102 - Dangerous default value {} as argument. Change to
context=None and add a 'context = context or {}' line.
[pylint] Fix W0102 - Dangerous default value [] as argument. Change to
args=None and add a 'args = args or []' line.
[pylint] Fix C0103 - Invalid name. Change names.
[pylint] Fix W0622 - Redefining built-in keys
keys  'id' and 'type'. rename keys to ids or obj_type.