ros installation error sudo rosdep init

Traceback (most recent call last):
  File "/usr/bin/rosdep", line 6, in <module>
    from pkg_resources import load_entry_point
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 3088, in <module>
    @_call_aside
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 3072, in _call_aside
    f(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 3101, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 574, in _build_master
    ws.require(__requires__)
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 892, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 778, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'rosdep==0.20.0' distribution was not found and is required by the application

Solution, change the default python version of the system

3 系统级修改
3.1 基于软链接
先删除默认的Python软链接：

sudo rm /usr/bin/python
1
然后创建一个新的软链接指向需要的Python版本：

sudo ln -s /usr/bin/python3.5 /usr/bin/python