dchr not defined error on 2012 script

This code worked before:-

### PLATFORM USING ###

ostag = bpy.app.build_platform

if (ostag == ‘Linux:64bit’ or ostag == ‘Linux:32bit’):
dchr=’/’
if (ostag == ‘Windows:64bit’ or ostag == ‘Windows:32bit’):
dchr=’\’

### PLATFORM USING ###

### DIRECTORY ###

curdir = bpy.data.filepath.rsplit(dchr,1)[0] +dchr <<<< error line!
print(curdir)

Why has this stopped working in the latest version of Blender or Python?