我想通过 R 命令从公共服务器下载文件（https://discovery.ucl.ac.uk/1575442/1/Palmisanoetal.zip）
temp <- tempfile()
utils::download.file(db_url, temp, method = 'curl')
这在我的 Ubuntu 18.04.3 LTS（仿生海狸）系统上不起作用。我收到以下错误：
curl: (60) SSL certificate problem: unable to get local issuer certificate
More details here: https://curl.haxx.se/docs/sslcerts.html
curl failed to verify the legitimacy of the server and therefore could not
establish a secure connection to it. To learn more about this situation and
how to fix it, please visit the web page mentioned above.
Error in utils::download.file(db_url, temp, method = "curl") :
'curl' call had …