fix deprecation warning

Author: psathyrella

python/treeutils.py

@@ -14,7 +14,7 @@
 import os
 import numpy
 import sys
-from distutils.version import StrictVersion
+from packaging.version import Version
 import dendropy
 import time
 import math
@@ -23,7 +23,7 @@
 import warnings
 import traceback
 from io import open
-if StrictVersion(dendropy.__version__) < StrictVersion('4.0.0'):  # not sure on the exact version I need, but 3.12.0 is missing lots of vital tree fcns
+if Version(dendropy.__version__) < Version('4.0.0'):  # not sure on the exact version I need, but 3.12.0 is missing lots of vital tree fcns
     raise RuntimeError("dendropy version 4.0.0 or later is required (found version %s)." % dendropy.__version__)
 import yaml
 try: