Return error exit code for "No lines…" error.

Fixes exussum12#72

Author: tomalec

src/functions.php

@@ -91,8 +91,10 @@ function handleOutput(array $lines, float $minimumPercentCovered, Output $output
 
 
     if ($coveredLines + $uncoveredLines == 0) {
-        error_log('No lines found!');
-        return;
+        throw new Exception(
+            'No lines found!',
+            3
+        );
     }
 
     $percentCovered = 100 * ($coveredLines / ($coveredLines + $uncoveredLines));