pin coolprop==6.8.0

Author: softwareengineerprogrammer

setup.py

@@ -77,7 +77,9 @@ def read(*names, **kwargs):
         'h5py',
         'scipy',
         'iapws',
-        'coolprop; python_version > "3.8"',
+        # coolprop 7.0.0 fails on macOS + Python > 3.8, see
+        # https://github.com/softwareengineerprogrammer/GEOPHIRES/actions/runs/16888333182/job/47841807973
+        'coolprop == 6.8.0; python_version > "3.8"',
         # coolprop > 6.7.0 fails on Python 3.8, see
         # https://github.com/softwareengineerprogrammer/GEOPHIRES/actions/runs/14599234458/job/40952924048?pr=69#step:5:302
         'coolprop==6.7.0; python_version == "3.8"',