chore(py3): remove outdated compatibility imports

Author: Rotzbua

exhale/graph.py

@@ -4038,11 +4038,7 @@ class view hierarchy.  It will be present in the file page it was declared in
         - Directories
         - Files
         '''
-        try:
-            from collections.abc import MutableMapping
-        except ImportError:
-            # TODO: remove when dropping python 2.7
-            from collections import MutableMapping
+        from collections.abc import MutableMapping
         class UnabridgedDict(MutableMapping):
             def __init__(self):
                 self.items = {}

testing/utils.py

@@ -10,11 +10,7 @@
 """
 
 from __future__ import unicode_literals
-try:
-    from collections.abc import Mapping
-except ImportError:
-    # TODO: remove when dropping python 2.7
-    from collections import Mapping
+from collections.abc import Mapping
 
 
 def deep_update(orig, override):