[gnome-software] trivial: Return a rewrite error if the local file is not found

[Richard Hughes <rhughes src gnome org>]

commit 16e1e14e2587f4a4aa1bbac3b5cab23bb42b8d7c
Author: Richard Hughes <richard hughsie com>
Date:   Thu May 11 15:19:05 2017 +0100

    trivial: Return a rewrite error if the local file is not found

 lib/gs-plugin.c |   14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)
---
diff --git a/lib/gs-plugin.c b/lib/gs-plugin.c
index f8f6f12..0f636a1 100644
--- a/lib/gs-plugin.c
+++ b/lib/gs-plugin.c
@@ -1340,10 +1340,18 @@ gs_plugin_download_rewrite_resource_uri (GsPlugin *plugin,
        g_autofree gchar *cachefn = NULL;
 
        /* local files */
-       if (g_str_has_prefix (uri, "/"))
-               return g_strdup (uri);
        if (g_str_has_prefix (uri, "file://"))
-               return g_strdup (uri + 7);
+               uri += 7;
+       if (g_str_has_prefix (uri, "/")) {
+               if (!g_file_test (uri, G_FILE_TEST_EXISTS)) {
+                       g_set_error (error,
+                                    GS_PLUGIN_ERROR,
+                                    GS_PLUGIN_ERROR_NOT_SUPPORTED,
+                                    "Failed to find file: %s", uri);
+                       return NULL;
+               }
+               return g_strdup (uri);
+       }
 
        /* get cache location */
        cachefn = gs_utils_get_cache_filename ("cssresource", uri,