https://wordpress.org/support/edit.php?id=8637302

class-connector-user.php

	public function callback_set_user_role( $user_id, $new_role, $old_roles ) {
		if ( empty( $old_roles ) ) {
			return;
		}

		$old_roles = array_values( $old_roles );

		global $wp_roles;

		$this->log(
			_x(
				'%1$s\'s role was changed from %2$s to %3$s',
				'1: User display name, 2: Old role, 3: New role',
				'stream'
			),
			array(
				'display_name' => get_user_by( 'id', $user_id )->display_name,
				'old_role'     => translate_user_role( $wp_roles->role_names[ $old_roles[0] ] ),
				'new_role'     => translate_user_role( $wp_roles->role_names[ $new_role ] ),
			),
			$user_id,
			'profiles',
			'updated'
		);
	}