More descriptive network connection issues message

[naoliv]

Could JOSM give a more descriptive message when we have connection/server side issues?
For example, with this:

2016-11-04 11:15:49.889 GRAVE: org.openstreetmap.josm.io.OsmApiException: ResponseCode=503, Error Body=<<h2>This website is under heavy load (queue full)</h2><p>Were sorry, too many people are accessing this website at the same time. Were working on this problem. Please try again later.</p>>
org.openstreetmap.josm.io.OsmApiException: ResponseCode=503, Error Body=<<h2>This website is under heavy load (queue full)</h2><p>Were sorry, too many people are accessing this website at the same time. Were working on this problem. Please try again later.</p>>
	at org.openstreetmap.josm.io.OsmServerReader.getInputStreamRaw(OsmServerReader.java:176)
	at org.openstreetmap.josm.io.OsmServerReader.getInputStreamRaw(OsmServerReader.java:110)
	at org.openstreetmap.josm.io.OsmServerReader.getInputStream(OsmServerReader.java:74)
	at org.openstreetmap.josm.io.OsmServerReader.getInputStream(OsmServerReader.java:57)
	at org.openstreetmap.josm.io.BoundingBoxDownloader.parseNotes(BoundingBoxDownloader.java:213)
	at org.openstreetmap.josm.actions.downloadtasks.DownloadNotesTask$DownloadBoundingBoxTask.realRun(DownloadNotesTask.java:149)
	at org.openstreetmap.josm.gui.PleaseWaitRunnable.doRealRun(PleaseWaitRunnable.java:93)
	at org.openstreetmap.josm.gui.PleaseWaitRunnable.run(PleaseWaitRunnable.java:141)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)

we only see a message saying Communication with the OSM server 'api.openstreetmap.org' timed out. Please retry later. (also note that the problem wasn't a time out here)

Maybe we could also have the Error Body displayed?

JOSM:

URL:http://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2016-11-04 01:16:28 +0100 (Fri, 04 Nov 2016)
Build-Date:2016-11-04 02:36:08
Revision:11215
Relative:URL: ^/trunk

Identification: JOSM/1.5 (11215 pt_BR) Linux Debian GNU/Linux testing (stretch)
Memory Usage: 394 MB / 10206 MB (146 MB allocated, but free)
Java version: 1.8.0_111-8u111-b14-2-b14, Oracle Corporation, OpenJDK 64-Bit Server VM
Screen: :0.0 1600x900, :0.1 1280x1024
Maximum Screen Size: 1600x1024
Java package: openjdk-8-jre:amd64-8u111-b14-2
Java ATK Wrapper package: libatk-wrapper-java:all-0.33.3-9
VM arguments: [-Dawt.useSystemAAFontSettings=on]
Dataset consistency test: No problems found