找到的解决方法--链接https://zhuanlan.zhihu.com/p/43345574
不能明白其中的编写python3程序

ERROR: Rosdep experienced an error: hostname 'raw.githubusercontent.com' doesn't match either of 'default.ssl.fastly.net', 'fastly.com', '.a.ssl.fastly.net', '.hosts.fastly.net', '.global.ssl.fastly.net', '.fastly.com', 'a.ssl.fastly.net', 'purge.fastly.net', 'mirrors.fastly.net', 'control.fastly.net', 'tools.fastly.net'
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: 0.18.0

Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/rosdep2/main.py", line 144, in rosdep_main
exit_code = _rosdep_main(args)
File "/usr/lib/python2.7/dist-packages/rosdep2/main.py", line 426, in _rosdep_main
return _no_args_handler(command, parser, options, args)
File "/usr/lib/python2.7/dist-packages/rosdep2/main.py", line 435, in _no_args_handler
return command_handlerscommand
File "/usr/lib/python2.7/dist-packages/rosdep2/main.py", line 579, in command_init
data = download_default_sources_list()
File "/usr/lib/python2.7/dist-packages/rosdep2/sources_list.py", line 331, in download_default_sources_list
f = urlopen(url, timeout=DOWNLOAD_TIMEOUT)
File "/usr/lib/python2.7/urllib2.py", line 154, in urlopen
return opener.open(url, data, timeout)
File "/usr/lib/python2.7/urllib2.py", line 429, in open
response = self._open(req, data)
File "/usr/lib/python2.7/urllib2.py", line 447, in _open
'_open', req)
File "/usr/lib/python2.7/urllib2.py", line 407, in _call_chain
result = func(*args)
File "/usr/lib/python2.7/urllib2.py", line 1241, in https_open
context=self._context)
File "/usr/lib/python2.7/urllib2.py", line 1195, in do_open
h.request(req.get_method(), req.get_selector(), req.data, headers)
File "/usr/lib/python2.7/httplib.py", line 1069, in request
self._send_request(method, url, body, headers)
File "/usr/lib/python2.7/httplib.py", line 1109, in _send_request
self.endheaders(body)
File "/usr/lib/python2.7/httplib.py", line 1065, in endheaders
self._send_output(message_body)
File "/usr/lib/python2.7/httplib.py", line 892, in _send_output
self.send(msg)
File "/usr/lib/python2.7/httplib.py", line 854, in send
self.connect()
File "/usr/lib/python2.7/httplib.py", line 1290, in connect
server_hostname=server_hostname)
File "/usr/lib/python2.7/ssl.py", line 369, in wrap_socket
_context=self)
File "/usr/lib/python2.7/ssl.py", line 599, in init
self.do_handshake()
File "/usr/lib/python2.7/ssl.py", line 836, in do_handshake
match_hostname(self.getpeercert(), self.server_hostname)
File "/usr/lib/python2.7/ssl.py", line 288, in match_hostname
% (hostname, ', '.join(map(repr, dnsnames))))
CertificateError: hostname 'raw.githubusercontent.com' doesn't match either of 'default.ssl.fastly.net', 'fastly.com', '.a.ssl.fastly.net', '.hosts.fastly.net', '.global.ssl.fastly.net', '.fastly.com', 'a.ssl.fastly.net', 'purge.fastly.net', 'mirrors.fastly.net', 'control.fastly.net', 'tools.fastly.net'