make exception message more precise

Author: dbu

src/Exception/MissingHostException.php

@@ -27,7 +27,7 @@ public static function missingHost($path)
         $msg = sprintf(
             'Path "%s" cannot be invalidated without a host. '
             . 'Either invalidate full URLs containing hostnames instead of paths '
-            . 'or configure the caching proxy class with a hostname.',
+            . 'or configure the caching proxy class with a hostname in the base path.',
             $path
         );