Update ui.bzl

Signed-off-by: Duck <70207455+entlein@users.noreply.github.com>

Author: entlein

bazel/ui.bzl

@@ -87,7 +87,9 @@ def _pl_webpack_library_impl(ctx):
         'pushd "$TMPPATH/src/ui" &> /dev/null',
         'tar -xzf "$BASE_PATH/{}"'.format(ctx.file.deps.path),
         'mv -f "$BASE_PATH/{}" src/pages/credits/licenses.json'.format(ctx.file.licenses.path),
-        "yarn build_prod",
+        "retval=0",
+        "output=`yarn build_prod 2>&1` || retval=$?",
+        '[ "$retval" -eq 0 ] || (echo $output; echo "Build Failed with Code: $retval"; exit $retval)',
         'cp dist/bundle.tar.gz "$BASE_PATH/{}"'.format(out.path),
     ] + ui_shared_cmds_finish