BusinessTemplate: do not export PythonScripts' Script_magic

This is used to trigger recompilation of bytecode, but we don't
export the byte code so we don't need to export it.
This also prevent diffs when the Script_magic changed, like it's the
case with Products.PythonScripts 4.2 , with commit 590125a (Force
recompilation of scripts., 2017-10-23).

product/ERP5/Document/BusinessTemplate.py

@@ -585,13 +585,21 @@ class BaseTemplateItem(Implicit, Persistent):
       # PythonScript covers both Zope Python scripts
       # and ERP5 Python Scripts
       if isinstance(obj, PythonScript):
-        # `expression_instance` is included so as to add compatibility for
-        # exporting older catalog methods which might have them as their
-        # properties or in their attribute dict.
-        attr_set.update(('func_code', '__code__',
-                         'func_defaults', '__defaults__',
-                         '_code', '_lazy_compilation', 'Python_magic',
-                         'expression_instance'))
+        attr_set.update(
+          (
+            '__code__',
+            'func_code',
+            '__defaults__',
+            'func_defaults',
+            '_code',
+            '_lazy_compilation',
+            'Python_magic',
+            'Script_magic',
+            # `expression_instance` is included so as to add compatibility for
+            # exporting older catalog methods which might have them as their
+            # properties or in their attribute dict.
+            'expression_instance',
+          ))
         for attr in 'errors', 'warnings', '_proxy_roles':
           if not obj.__dict__.get(attr, 1):
             delattr(obj, attr)