Import MutableMapping from collections.abc where possible

Author: scottgigante

igraph/utils.py

@@ -6,7 +6,10 @@
 """
 
 from contextlib import contextmanager
-from collections import MutableMapping
+try:
+    from collections.abc import MutableMapping
+except ImportError:
+    from collections import MutableMapping
 from ctypes import c_double, sizeof
 from itertools import chain