Better assertion for required message
Better assertion for required message

- In each case, this should be the only message; use `assertSame()`.

akomm/zend-inputfilter,Maks3w/zend-inputfilter,zendframework/zend-inputfilter,MadCat34/zend-inputfilter,zf2timo/zend-inputfilter,Blinden/zend-inputfilter,stefanotorresi/zend-inputfilter