wic: fix WicError message

* add missing % to print the values instead of:
  | INFO: Build artifacts not found, exiting.
  | INFO:   (Please check that the build artifacts for the machine
  | INFO:    selected in local.conf actually exist and that they
  | INFO:    are the correct artifacts for the image (.wks file)).
  |
  | ERROR: ("The artifact that couldn't be found was %s:\n  %s", 'kernel-dir', '/OE/build/deploy/images/qemux86-64')

(From OE-Core rev: e104c2b1273d8c5bd97893f318bf2a2699ef7f2d)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/wic

@@ -209,7 +209,7 @@ def wic_create_subcommand(options, usage_str):
             logger.info("  (Please check that the build artifacts for the machine")
             logger.info("   selected in local.conf actually exist and that they")
             logger.info("   are the correct artifacts for the image (.wks file)).\n")
-            raise WicError("The artifact that couldn't be found was %s:\n  %s", not_found, not_found_dir)
+            raise WicError("The artifact that couldn't be found was %s:\n  %s" % (not_found, not_found_dir))
 
     krootfs_dir = options.rootfs_dir
     if krootfs_dir is None: