Fixed #260

flask_admin/contrib/mongoengine/helpers.py

+from mongoengine import ValidationError
+from flask.ext.admin._compat import itervalues, as_unicode
+
+
 def make_gridfs_args(value):
     args = {
         'id': value.grid_id,
@@ -23,3 +27,10 @@ def make_thumb_args(value):
         return args
     else:
         return make_gridfs_args(value)
+
+
+def format_error(error):
+    if isinstance(error, ValidationError):
+        return '. '.join(itervalues(error.to_dict()))
+
+    return as_unicode(error)

flask_admin/contrib/mongoengine/view.py

@@ -19,6 +19,7 @@ from .filters import FilterConverter, BaseMongoEngineFilter
 from .form import get_form, CustomModelConverter
 from .typefmt import DEFAULT_FORMATTERS
 from .tools import parse_like_term
+from .helpers import format_error
 
 
 SORTABLE_FIELDS = set((
@@ -357,7 +358,8 @@ class ModelView(BaseModelView):
             self._on_model_change(form, model, True)
             model.save()
         except Exception as ex:
-            flash(gettext('Failed to create model. %(error)s', error=str(ex)),
+            flash(gettext('Failed to create model. %(error)s',
+                          error=format_error(ex)),
                   'error')
             logging.exception('Failed to create model')
             return False
@@ -380,7 +382,8 @@ class ModelView(BaseModelView):
             self._on_model_change(form, model, False)
             model.save()
         except Exception as ex:
-            flash(gettext('Failed to update model. %(error)s', error=str(ex)),
+            flash(gettext('Failed to update model. %(error)s',
+                          error=format_error(ex)),
                   'error')
             logging.exception('Failed to update model')
             return False
@@ -401,7 +404,8 @@ class ModelView(BaseModelView):
             model.delete()
             return True
         except Exception as ex:
-            flash(gettext('Failed to delete model. %(error)s', error=str(ex)),
+            flash(gettext('Failed to delete model. %(error)s',
+                          error=format_error(ex)),
                   'error')
             logging.exception('Failed to delete model')
             return False