Fixed return value of rolling stones generator.

robotgame/logic/rollingstone.py

@@ -79,7 +79,7 @@ def generate_simple_playfield(width, height, nturns, nstones,
       * the playfield is completable in nturns or less
       * the playfield has at most nstones stones
 
-    Return (playfield : {(x, y): Direction | Blocker | None},
+    Return (playfield : {(x, y): Direction | Blocker},
             steps : int)
     where (x, y) : (int, int)
 
@@ -145,6 +145,7 @@ def generate_simple_playfield(width, height, nturns, nstones,
 
     used_fields = _fields_from_turns(turns)
     playfield = {}
+    del turns[-1]
     for p, d in turns:
         playfield[p] = d
     emptys = set(itertools.product(range(width),