WordPress at a glance
filter is not described

update_feedback filter-hook . WP 1.0

Outout the failure error as a normal feedback, and not as an error:

Usage

add_filter( 'update_feedback', 'filter_function_name_87' );
function filter_function_name_87( $download_error_message ){
	// filter...

	return $download_error_message;
}
$download_error_message
-

Where the hook is called

Core_Upgrader::upgrade()
update_feedback
update_core()
update_feedback
wp-admin/includes/class-core-upgrader.php 130
apply_filters( 'update_feedback', $download->get_error_message() );
wp-admin/includes/class-core-upgrader.php 193
apply_filters( 'update_feedback', $result );
wp-admin/includes/class-core-upgrader.php 196
apply_filters( 'update_feedback', $this->strings['start_rollback'] );
wp-admin/includes/update-core.php 902
apply_filters( 'update_feedback', __( 'Verifying the unpacked files…' ) );
wp-admin/includes/update-core.php 971
apply_filters( 'update_feedback', __( 'Preparing to install the latest version…' ) );
wp-admin/includes/update-core.php 1033
apply_filters( 'update_feedback', __( 'Enabling Maintenance mode…' ) );
wp-admin/includes/update-core.php 1041
apply_filters( 'update_feedback', __( 'Copying the required files…' ) );
wp-admin/includes/update-core.php 1128
apply_filters( 'update_feedback', __( 'Disabling Maintenance mode…' ) );
wp-admin/includes/update-core.php 1217
apply_filters( 'update_feedback', __( 'Upgrading database…' ) );

Where the hook is used (in WP core)

wp-admin/includes/class-wp-automatic-updater.php 279
add_filter( 'update_feedback', array( $skin, 'feedback' ) );
wp-admin/includes/deprecated.php 1155
add_filter('update_feedback', $feedback);
wp-admin/includes/deprecated.php 1178
add_filter('update_feedback', $feedback);
wp-admin/includes/deprecated.php 1200
add_filter('update_feedback', $feedback);
wp-admin/update-core.php 557
add_filter( 'update_feedback', 'show_message' );