http: Log errors instead of dying for HTTP startup.

docs/changelog.rst

@@ -69,6 +69,11 @@ v0.20.0 (UNRELEASED)
   make sense for a server such as Mopidy. Currently the only way to find out if
   it is in use and will be missed is to go ahead and remove it.
 
+**HTTP**
+
+- Log error while starting HTTP apps instead letting the HTTP server thread
+  die. (Fixes: :issue:`875`)
+
 
 v0.19.5 (UNRELEASED)
 ====================

mopidy/http/actor.py

@@ -129,11 +129,16 @@ class HttpServer(threading.Thread):
     def _get_app_request_handlers(self):
         result = []
         for app in self.apps:
+            try:
+                request_handlers = app['factory'](self.config, self.core)
+            except Exception:
+                logger.exception('Loading %s failed.', app['name'])
+                continue
+
             result.append((
                 r'/%s' % app['name'],
                 handlers.AddSlashHandler
             ))
-            request_handlers = app['factory'](self.config, self.core)
             for handler in request_handlers:
                 handler = list(handler)
                 handler[0] = '/%s%s' % (app['name'], handler[0])