No web proxy:
$ openssl s_client -showcerts -connect pypi.python.org:443 </dev/null >/dev/null
depth=2 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert High Assurance EV Root CA
verify return:1
depth=1 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert High Assurance CA-3
verify return:1
depth=0 C = US, ST = California, L = San Francisco, O = "Fastly, Inc.", CN = *.a.ssl.fastly.net
verify return:1
DONE
Web proxy:
$ openssl s_client -showcerts -connect pypi.python.org:443 </dev/null >/dev/null
depth=1 /C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance CA-3
verify error:num=20:unable to get local issuer certificate
verify return:0
DONE