As mentioned in guix-bug #52606 (https://debbugs.gnu.org/cgi/bugreport.cgi?bug=52606) the OpenSCAD workbench in FreeCAD depends on this dependecy to work.

Signed-off-by: Jacob Hrbek <kreyren@rixotstudio.cz>
---
 gnu/packages/engineering.scm | 1 +
 1 file changed, 1 insertion(+)

diff --git a/gnu/packages/engineering.scm b/gnu/packages/engineering.scm
index edc0f51d8d..823b4788d7 100644
--- a/gnu/packages/engineering.scm
+++ b/gnu/packages/engineering.scm
@@ -2433,6 +2433,7 @@ (define-public freecad
            python-gitpython
            python-matplotlib
            python-pivy
+	   python-ply
            python-pyside-2
            python-pyyaml
            python-shiboken-2
--
2.34.0