Fix python 3 imports

bob/bio/base/utils/io.py

 import os
 import tempfile
 import tarfile
-import collections  # this is needed for the sphinx documentation
+try:  # this is needed for the sphinx documentation
+  from collections.abc import Callable, Iterable
+except ImportError:
+  from collections import Callable, Iterable
 import functools  # this is needed for the sphinx documentation
 import numpy
 import logging
@@ -182,9 +185,9 @@ def _generate_features(reader, paths):
 
   Parameters
   ----------
-  reader : collections.Callable
+  reader : Callable
       See the documentation of :py:func:`vstack_features`.
-  paths : collections.Iterable
+  paths : Iterable
       See the documentation of :py:func:`vstack_features`.
 
   Yields
@@ -270,14 +273,14 @@ def vstack_features(reader, paths, same_size=False):
 
   Parameters
   ----------
-  reader : collections.Callable
+  reader : Callable
       The function to load the features. The function should only take one
       argument being the path to the features. Use
       :any:`functools.partial` to accommodate your reader to this format.
       The features returned by ``reader`` are expected to have the same
       :py:class:`numpy.dtype` and the same shape except for their first
       dimension. First dimension is should correspond to the number of samples.
-  paths : collections.Iterable
+  paths : Iterable
       An iterable of paths to iterate on. Whatever is inside path is given to
       ``reader``. If ``same_size`` is ``True``, ``len(paths)`` must be valid.
   same_size : :obj:`bool`, optional