Clean up output and test

Author: danielbachhuber

features/cron.feature

@@ -389,7 +389,7 @@ Feature: Manage WP-Cron events and schedules
       """
     And I run `wp eval-file update.php`
 
-    When I run `wp cron event list`
+    When I try `wp cron event list`
     Then STDOUT should contain:
       """
       postindexer_secondpass_cron

src/Cron_Event_Command.php

@@ -452,7 +452,7 @@ protected static function get_cron_events( $is_due_now = false ) {
 
 			// Incorrectly registered cron events can produce a string key.
 			if ( is_string( $time ) ) {
-				WP_CLI::warning( sprintf( 'Ignoring invalid cron event ("%s").', $time ) );
+				WP_CLI::warning( sprintf( 'Ignoring incorrectly registered cron event "%s".', $time ) );
 				continue;
 			}