i.pansharpen: grass.decode stdout (#416)

scripts/i.pansharpen/i.pansharpen.py

@@ -549,7 +549,7 @@ def matchhist(original, target, matched):
         # calculate number of cells for each grey value for for each image
         stats_out = grass.pipe_command('r.stats', flags='cin', input=img,
                                        sep=':')
-        stats = stats_out.communicate()[0].split('\n')[:-1]
+        stats = grass.decode(stats_out.communicate()[0]).split('\n')[:-1]
         stats_dict = dict(s.split(':', 1) for s in stats)
         total_cells = 0  # total non-null cells
         for j in stats_dict: