Melchior FRANZ:

There are constructors for sg_io_exception that don't initialize the
location. In this case getFormattedMessage does still output an extra
line with " at" followed by ... nothing. Looks silly.

simgear/structure/exception.cxx

@@ -229,8 +229,11 @@ const string
 sg_io_exception::getFormattedMessage () const
 {
   string ret = getMessage();
-  ret += "\n at ";
-  ret += getLocation().asString();
+  string loc = getLocation().asString();
+  if (loc.length()) {
+    ret += "\n at ";
+    ret += loc;
+  }
   return ret;
 }