Sounds like you are trying to create a widget using either brackets or the widget generator. When you do, the id of the widget changes (becomes something like CustomWidget.widget.CustomWidget). But... the test-project has a widget with id WidgetName.widget.WidgetName, and this one he cannot find anymore.
Remove the custom widget from your test-project and add your own. :-)
You probably have a custom widget that is misbehaving. When you deploy locally you could check the logs in deployment\log. There you can see which widget is causing the error.