SSLError: (‘The read operation timed out‘,) 解决方法

$ sudo rosdep init

ERROR: Rosdep experienced an error: ('The read operation timed out',)
Please go to the rosdep page [1] and file a bug report with the stack trace below.
[1] : http://www.ros.org/wiki/rosdep

rosdep version: 0.21.0

Traceback (most recent call last):
  ....
  File "/usr/lib/python2.7/ssl.py", line 754, in recv
    return self.read(buflen)
  File "/usr/lib/python2.7/ssl.py", line 641, in read
    v = self._sslobj.read(len)
SSLError: ('The read operation timed out',)

原因多半是没有安装 pip ，或者 pip 版本不对造成的。

安装 pip

sudo apt install python-pip

或者升级 pip

sudo pip install --upgrade -i https://pypi.tuna.tsinghua.edu.cn/simple pip
sudo pip3 install --upgrade -i ttps://pypi.tuna.tsinghua.edu.cn/simple pip