[install] use an older version of cx_freeze

See marcelotduarte/cx_Freeze#652

Author: fabiencastan

dev_requirements.txt

@@ -1,7 +1,8 @@
 # packaging
 
 cx_Freeze==5.1.1;python_version<"3.5"
-cx_Freeze;python_version>="3.5"
+# Problem with cx_freeze-6.2, see https://github.com/marcelotduarte/cx_Freeze/issues/652
+cx_Freeze==6.1;python_version>="3.5"
 
 # testing
 pytest