Make exception_handler handle all exception types

Previously exception_handler expected exceptions to have name and code attributes. We now default to 'Internal error' and 500 respectively if these attributes do not exist.

backdrop/read/api.py

@@ -53,7 +53,8 @@ def default(self, obj):
 @app.errorhandler(404)
 def exception_handler(e):
     app.logger.exception(e)
-    return jsonify(status='error', message=e.name), e.code
+    return jsonify(status='error',
+                   message=getattr(e, 'name', 'Internal error')), getattr(e, 'code', 500)
 
 
 @app.route('/_status', methods=['GET'])