fix!: handle errors properly

src/ChildException.php

@@ -4,5 +4,23 @@ declare(strict_types=1);
 
 namespace Nih\CommandBuilder;
 
-class ChildException extends CommandException
-{}
+/**
+ * A PHP error occured during an operation on a process resource.
+ */
+final class ChildException extends CommandException
+{
+    public static function handleError(
+        int $severity,
+        string $message,
+        string $filename,
+        int $line,
+    ): never {
+        throw new self(
+            message: $message,
+            code: 0,
+            severity: $severity,
+            filename: $filename,
+            line: $line,
+        );
+    }
+}