Fix #289

Tweak the second keyboard robot recipe so it detects keyboards and
doesn't throw exceptions on unknown keys. Also add a note to the recipe
that it won't work over remote connections like SSH.

docs/recipes.rst

@@ -345,11 +345,16 @@ Use up/down/left/right keys to control a robot:
     recipe will *not* work in environments like IDLE.
 
 If you prefer a version that works under IDLE, the following recipe should
-suffice, but will require that you install the evdev library with ``sudo pip3
-install evdev`` first:
+suffice:
 
 .. literalinclude:: examples/robot_keyboard_2.py
 
+.. note::
+
+    This recipe uses the third-party ``evdev`` module. Install this library
+    with ``sudo pip3 install evdev`` first. Be aware that ``evdev`` will only
+    work with local input devices; this recipe will *not* work over SSH.
+
 
 Motion sensor robot
 ===================