diff -ur patsy-0.5.1/patsy/constraint.py patsy-0.5.1-p39/patsy/constraint.py

--- patsy-0.5.1/patsy/constraint.py	2018-10-28 03:34:36.000000000 +0100

+++ patsy-0.5.1-p39/patsy/constraint.py	2020-01-26 10:58:58.047555461 +0100

@@ -10,7 +10,10 @@

 __all__ = ["LinearConstraint"]

 import re

-from collections import Mapping

+try:

+    from collections.abc import Mapping

+except ImportError:

+    from collections import Mapping

 import six

 import numpy as np

 from patsy import PatsyError