drush mi almost always returns 0 as an exit code.

I was going to run something along the lines of `drush mi my_migration || echo "FAILURE!"`... or have my CI test for the exit code to find when there were failures importing... instead... I'm getting an exit code of 0 even withs something like this:

Processed 4953 items (4270 created, 2 updated, 23 failed, 658 ignored) - done with 'upgrade_d7_taxonomy_term'

I would expect that if you have any "failed" you would have an exit code > 0... particularly when my migration is throwing error output like the following

SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'name' cannot be null: INSERT INTO {taxonomy_term_field_data}  [error]
(tid, vid, langcode, name, description__value, description__format, weight, changed, default_langcode) VALUES
(:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3,
:db_insert_placeholder_4, :db_insert_placeholder_5, :db_insert_placeholder_6, :db_insert_placeholder_7,
:db_insert_placeholder_8); Array
(
    [:db_insert_placeholder_0] => 8426
    [:db_insert_placeholder_1] => person_title
    [:db_insert_placeholder_2] => en
    [:db_insert_placeholder_3] =>
    [:db_insert_placeholder_4] =>
    [:db_insert_placeholder_5] =>
    [:db_insert_placeholder_6] => 10
    [:db_insert_placeholder_7] => 1463413778
    [:db_insert_placeholder_8] => 1
)