use collections.abc for Mapping (#2750)

* use collections.abc.Mapping when available

* ignore py2, tox -e py27-linux revealed setup.py requires python 3.5

* use collections.abc.Iterable

gensim/corpora/dictionary.py

@@ -8,7 +8,8 @@
 
 from __future__ import with_statement
 
-from collections import Mapping, defaultdict
+from collections import defaultdict
+from collections.abc import Mapping
 import sys
 import logging
 import itertools

gensim/models/doc2vec.py

@@ -70,7 +70,8 @@
 except ImportError:
     from Queue import Queue  # noqa:F401
 
-from collections import namedtuple, defaultdict, Iterable
+from collections import namedtuple, defaultdict
+from collections.abc import Iterable
 from timeit import default_timer
 
 from numpy import zeros, float32 as REAL, empty, ones, \

gensim/models/fasttext.py

@@ -285,7 +285,7 @@
 import numpy as np
 from numpy import ones, vstack, float32 as REAL
 import six
-from collections import Iterable
+from collections.abc import Iterable
 
 import gensim.models._fasttext_bin
 

gensim/test/test_corpora_dictionary.py

@@ -7,8 +7,7 @@
 Unit tests for the `corpora.Dictionary` class.
 """
 
-
-from collections import Mapping
+from collections.abc import Mapping
 from itertools import chain
 import logging
 import unittest