title: Reasons to fail a build
body: <p>As a build engineer, I'm constantly looking for new and interesting ways to improve our build process - and that includes looking for new and interesting ways to fail our builds!</p>
  
  <p>I have yet to find a canonical list of reasons to fail a build ... so I figure it's time to get one created. With that in mind:</p>
  
  <p><strong>What build-time checks - both obvious and creative - have you seen fail builds?</strong></p>