Add python3-defusedxml to dependencies

Author: chennes

snap/snapcraft.yaml

@@ -213,6 +213,7 @@ parts:
       - python3-yaml # FEM
       - python3-numba # FEM (fcFEM)
       - python3-scipy # FEM
+      - python3-defusedxml # Addon Manager
       - python3-numpy
       - python3-matplotlib
       - python3-six