luci-app-attendedsysupgrade: add more robust handling of downloads

Check various aspects of the overview and revision downloads from
the sysupgrade site, giving the user better error messages when
things go wrong.

Partially addresses issue #7687 with respect to diagnosis, but not
root cause.

Signed-off-by: Eric Fahlgren <ericfahlgren@gmail.com>

Author: efahl

applications/luci-app-attendedsysupgrade/htdocs/luci-static/resources/view/attendedsysupgrade/overview.js

@@ -87,23 +87,22 @@ return view.extend({
 		let changes, target_revision;
 
 		await Promise.all([
-			request.get(overview_url).then(
-				(response) => {
-					let json = response.json();
-					changes = json.branches[get_branch(version)].package_changes;
-				},
-				(failed) => {
-					ui.addNotification(null, E('p', _(`Get overview failed ${failed}`)));
-				}
-			),
-			request.get(revision_url).then(
-				(response) => {
-					target_revision = get_revision_count(response.json().revision);
-				},
-				(failed) => {
-					ui.addNotification(null, E('p', _(`Get revision failed ${failed}`)));
-				}
-			),
+			request.get(overview_url)
+				.then(response => response.json())
+				.then(json => json.branches)
+				.then(branches => branches[get_branch(version)])
+				.then(branch => { changes = branch.package_changes; })
+				.catch(error => {
+					throw Error(`Get overview failed:<br>${overview_url}<br>${error}`);
+				}),
+
+			request.get(revision_url)
+				.then(response => response.json())
+				.then(json => json.revision)
+				.then(revision => { target_revision = get_revision_count(revision); })
+				.catch(error => {
+					throw Error(`Get revision failed:<br>${revision_url}<br>${error}`);
+				}),
 		]);
 
 		for (const change of changes) {
@@ -595,6 +594,10 @@ return view.extend({
 												}, this);
 												poll.add(this.pollFn, 5);
 												poll.start();
+											})
+											.catch(error => {
+											    ui.addNotification(null, E('p', error.message));
+											    ui.hideModal();
 											});
 										});
 									}),