this test is failing for me ..

```
1) ZendDiagnosticsTest\DiskFreeTest::testSpaceWithStringConversion
Failed asserting that ZendDiagnostics\Result\Failure Object (...) is an instance of class "ZendDiagnostics\Result\SuccessInterface".

/Users/lsmith/htdocs/symfony-standard/vendor/zendframework/zenddiagnostics/tests/ZendDiagnosticsTest/DiskFreeTest.php:139
```