Fix more python 3 deprecations

Author: jasongrout

ipywidgets/widgets/interaction.py

@@ -246,7 +246,7 @@ def update(self, *args):
         except Exception as e:
             ip = get_ipython()
             if ip is None:
-                self.log.warn("Exception in interact callback: %s", e, exc_info=True)
+                self.log.warning("Exception in interact callback: %s", e, exc_info=True)
             else:
                 ip.showtraceback()
         finally:

ipywidgets/widgets/tests/test_interaction.py

@@ -249,7 +249,8 @@ def test_iterable_tuple():
     check_widgets(c, lis=d)
 
 def test_mapping():
-    from collections import Mapping, OrderedDict
+    from collections.abc import Mapping
+    from collections import OrderedDict
     class TestMapping(Mapping):
         def __init__(self, values):
             self.values = values