Use set_marker() in legend_handler.py. Closes matplotlib#412

Author: leejjoon

lib/matplotlib/legend_handler.py

@@ -196,7 +196,7 @@ def create_artists(self, legend, orig_handle,
         #legline.set_clip_box(None)
         #legline.set_clip_path(None)
         legline.set_drawstyle('default')
-        legline.set_marker('None')
+        legline.set_marker("")
 
 
         legline_marker = Line2D(xdata_marker, ydata[:len(xdata_marker)])