Add patch to fix leaking translations

Currently, when a translatable fields value is set via the admin
intrface in a specific lungage (e.g. title_de) , that value leaks into
the translated field of the language of the session (e.h. title_en).

This patch tries to fix this.

patches/modeltranslations-Don-t-leak-into-current-language.patch

@@ -0,0 +1,49 @@
+From 8fa955600d5653af7ee0c552fb18005a0dd9e043 Mon Sep 17 00:00:00 2001
+From: Donald Buczek <buczek@molgen.mpg.de>
+Date: Mon, 13 Jan 2020 16:43:34 +0100
+Subject: [PATCH] modeltranslations: Don't leak into current language
+
+Disable the implicit setting of the translation field from
+the translated field ( Rule 2 of [1] ) if we come from
+clean_fields. See [2]
+
+[1] https://django-modeltranslation.readthedocs.io/en/latest/usage.html#rules-for-translated-field-access ) if we come from clean_fields
+[2] https://github.com/deschler/django-modeltranslation/issues/382
+---
+ lib/python3.7/site-packages/modeltranslation/fields.py     | 2 +-
+ lib/python3.7/site-packages/modeltranslation/translator.py | 6 +++++-
+ 2 files changed, 6 insertions(+), 2 deletions(-)
+
+diff --git a/lib/python3.7/site-packages/modeltranslation/fields.py b/lib/python3.7/site-packages/modeltranslation/fields.py
+index d3c5a42..2ff0d83 100644
+--- a/lib/python3.7/site-packages/modeltranslation/fields.py
++++ b/lib/python3.7/site-packages/modeltranslation/fields.py
+@@ -314,7 +314,7 @@ class TranslationFieldDescriptor(object):
+         instance.__dict__[self.field.name] = value
+         if isinstance(self.field, fields.related.ForeignKey):
+             instance.__dict__[self.field.get_attname()] = None if value is None else value.pk
+-        if getattr(instance, '_mt_init', False):
++        if getattr(instance, '_mt_init', False) or getattr(instance, '_mt_disable', False):
+             # When assignment takes place in model instance constructor, don't set value.
+             # This is essential for only/defer to work, but I think it's sensible anyway.
+             return
+diff --git a/lib/python3.7/site-packages/modeltranslation/translator.py b/lib/python3.7/site-packages/modeltranslation/translator.py
+index 901f701..d58dd55 100644
+--- a/lib/python3.7/site-packages/modeltranslation/translator.py
++++ b/lib/python3.7/site-packages/modeltranslation/translator.py
+@@ -267,7 +267,11 @@ def patch_clean_fields(model):
+                 if orig_field_name in exclude:
+                     field.save_form_data(self, value, check=False)
+             delattr(self, '_mt_form_pending_clear')
+-        old_clean_fields(self, exclude)
++        setattr(self, '_mt_disable', True)
++        try:
++            old_clean_fields(self, exclude)
++        finally:
++            setattr(self, '_mt_disable', False)
+     model.clean_fields = new_clean_fields
+
+
+-- 
+2.24.1
+