Add exceptions

src/Exception/GeocodeException.php

@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pcm\GeocodeBundle\Exception;
+
+class GeocodeException extends \RuntimeException
+{
+    public function __construct(string $postcode, string $message)
+    {
+        $formattedMessage = sprintf("Failed to geocode a postcode \"%s\": %s", $postcode, $message);
+
+        parent::__construct($formattedMessage);
+    }
+}
+