use nicer syntax to handle deprecated import

Author: mkcor

dash/development/base_component.py

@@ -1,15 +1,15 @@
 import abc
 import inspect
 import sys
-try:
-    from collections.abc import MutableSequence
-except ImportError:
-    from collections import MutableSequence
-
 import six
 
 from .._utils import patch_collections_abc
 
+if six.PY2:
+    from collections import MutableSequence
+else:
+    from collections.abc import MutableSequence
+
 
 # pylint: disable=no-init,too-few-public-methods
 class ComponentRegistry: