Fix Exception: Cannot find reverse relation for model

SQLAlchemy 2.0.2 removed the invocation of registry.configure() from
Mapper.iterate_properties causing this problem.

sqlalchemy.orm.registry.configure() was added in 1.4.0b2.

Observed as test failures in:

flask_admin/tests/sqla/test_basic.py
flask_admin/tests/sqla/test_form_rules.py
flask_admin/tests/sqla/test_inlineform.py

flask_admin/contrib/sqla/form.py

@@ -669,6 +669,7 @@ def _calculate_mapping_key_pair(self, model, info):
 
         reverse_prop = None
 
+        model.registry.configure()
         for prop in target_mapper.iterate_properties:
             if hasattr(prop, 'direction') and prop.direction.name in ('MANYTOONE', 'MANYTOMANY'):
                 if issubclass(model, prop.mapper.class_):

flask_admin/contrib/sqla/view.py

@@ -366,6 +366,7 @@ def _get_model_iterator(self, model=None):
         if model is None:
             model = self.model
 
+        model.registry.configure()
         return model._sa_class_manager.mapper.iterate_properties
 
     def _apply_path_joins(self, query, joins, path, inner_join=True):

requirements-min.txt

@@ -1,7 +1,7 @@
 Flask==1.1.1
 itsdangerous==2.0.1
 werkzeug==0.16.1
-sqlalchemy==1.3.12
+sqlalchemy==1.4.0
 MarkupSafe==1.1.0
 jinja2==2.10.1
 Flask-SQLAlchemy==2.1