File "/usr/lib/python2.7/dist-packages/rospkg/distro.py", line 44, in <module>
import yaml
File "/usr/lib/python3/dist-packages/yaml/init.py", line 284
class YAMLObject(metaclass=YAMLObjectMetaclass):
^
SyntaxError: invalid syntax

同问，运行roscore就报这个错误，怎么解决啊？