Don't silence exceptions in production mode.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/metadata/views.py

@@ -139,12 +139,31 @@ class DocumentMetadataAddView(MultipleObjectFormActionView):
 
     def object_action(self, form, instance):
         for metadata_type in form.cleaned_data['metadata_type']:
+            try:
                 document_metadata, created = DocumentMetadata.objects.get_or_create(
                     document=instance,
                     metadata_type=metadata_type,
                     defaults={'value': ''}
                 )
-
+            except Exception as exception:
+                #if getattr(settings, 'DEBUG', False):
+                #    raise
+                #else:
+                messages.error(
+                    self.request,
+                    _(
+                        'Error adding metadata type '
+                        '"%(metadata_type)s" to document: '
+                        '%(document)s; %(exception)s'
+                    ) % {
+                        'metadata_type': metadata_type,
+                        'document': instance,
+                        'exception': ', '.join(
+                            getattr(exception, 'messages', exception)
+                        )
+                    }
+                )
+            else:
                 if created:
                     messages.success(
                         self.request,