Set readonly state conditional.

This commit refs #2600

productive_process.py

@@ -24,6 +24,14 @@ class ProductiveProcDocMixin(object):
     productive_process = fields.Many2One('productive.process',
         'Productive process', ondelete='RESTRICT', required=True, select=True)
 
+    @classmethod
+    def __setup__(cls):
+        super(ProductiveProcDocMixin, cls).__setup__()
+        if getattr(cls, 'state', None):
+            cls.productive_process.states['readonly'] = (
+                Eval('state') != 'draft')
+            cls.productive_process.depends.append('state')
+
     @staticmethod
     def default_productive_process():
         transaction = Transaction()