Tweak error message

Author: sebastianbergmann

src/Util/ThrowableToStringMapper.php

@@ -13,6 +13,7 @@
 use PHPUnit\Framework\ExpectationFailedException;
 use PHPUnit\Framework\PhptAssertionFailedError;
 use PHPUnit\Framework\SelfDescribing;
+use PHPUnit\Runner\ErrorException;
 use Throwable;
 
 /**
@@ -22,6 +23,10 @@ final class ThrowableToStringMapper
 {
     public static function map(Throwable $t): string
     {
+        if ($t instanceof ErrorException) {
+            return $t->getMessage();
+        }
+
         if ($t instanceof SelfDescribing) {
             $buffer = $t->toString();