>>> bm.verts[127][bmli]
Traceback (most recent call last):
File "<blender_console>", line 1, in <module>
ValueError: Layer/Element type mismatch, expected (BMVert)� got layer type (BMLoop)�H

(diamond shape with question mark in it + rectangles indicating bad characters)

If they are \t \n or something, they should be converted for console