[IMP] web: log module loading issues even when they throw a real error

Previously, when an Error was thrown inside an async module, that error
would not cause boot.js to log information about missing, failed or
rejected modules. This is because we were only using guardedCatch to
mark modules returning a rejected promise with something other than an
error as rejected, but the case where a real error was thrown was not
handled, which left the job to be forever pending.

This commit fixes that by catching real errors after the previous
processing, and treats it like an error in a synchronous module.

addons/web/static/src/boot.js

@@ -280,14 +280,16 @@
             var require = makeRequire(job);
 
             var jobExec;
+            function onError(e) {
+                job.error = e;
+                console.error(`Error while loading ${job.name}: ${e.message}`, e);
+            }
             var def = new Promise(function (resolve) {
                 try {
                     jobExec = job.factory.call(null, require);
                     jobs.splice(jobs.indexOf(job), 1);
                 } catch (e) {
-                    job.error = e;
-                    console.error(e);
-                    console.error(`Error while loading ${job.name}: ${e.message}`);
+                    onError(e);
                 }
                 if (!job.error) {
                     Promise.resolve(jobExec)
@@ -299,6 +301,11 @@
                         .guardedCatch(function (e) {
                             job.rejected = e || true;
                             jobs.push(job);
+                        })
+                        .catch(function (e) {
+                            if (e instanceof Error) {
+                                onError(e);
+                            }
                             resolve();
                         });
                 } else {