docs

apps/gpssetup/README.md

@@ -86,6 +86,19 @@ require("gpssetup").setPowerMode().then(function() {
 });
 ```
 
+**Note:** It's not guaranteed that the user will have installed the `gpssetup`
+app/module. It might be worth checking for its existence by surrounding the
+`require` call with `try...catch` block.
+
+```
+var gpssetup;
+try {
+  gpssetup = require("gpssetup")
+} catch(e) {
+  E.showMessage("gpssetup\nnot installed");
+}
+```
+
 ## References
 
 * [UBLOX M8 Receiver Data Sheet](https://www.u-blox.com/sites/default/files/products/documents/u-blox8-M8_ReceiverDescrProtSpec_%28UBX-13003221%29.pdf)