使用安装第三方插件的方式安装pycurl：pip3 install pycurl
报错提示如下：
Curl is configured to use SSL, but we have not been able to determine which SSL backend it is using. Please see PycURL documentation for how to specify the SSL backend manually.'
解决方案：
$ export LDFLAGS=-L/usr/local/opt/openssl/lib
$ export CPPFLAGS=-I/usr/local/opt/openssl/include
$ export PYCURL_SSL_LIBRARY=openssl
$ pip3 install pycurl