输入./.repo/repo/repo sync 命令，出现ImportError: No module named subcmds，请问怎么解决

wang@ubuntu:~/rowboat_android/TI_Android_GingerBread_2_3_4_AM335x_Sources$ ./.repo/repo/repo sync

Traceback (most recent call last):

 File "/home/wang/rowboat_android/TI_Android_GingerBread_2_3_4_AM335x_Sources/.repo/repo/main.py", line 47, in <module>

   from subcmds import all as all_commands

ImportError: No module named subcmds

wang@ubuntu:~/rowboat_android/TI_Android_GingerBread_2_3_4_AM335x_Sources$