Failed and print "unknown protocol" when Jenkins is using https

[sicheng20]

I got this error when I start jenkins_exporter.py:
requests.exceptions.SSLError: HTTPSConnectionPool(host='10.7.240.14', port=31296): Max retries exceeded with url: /api/json?tree=jobs%5BfullName%2Curl%2ClastBuild%5BfullName%2Cnumber%2Ctimestamp%2Cduration%2Cactions%5BqueuingDurationMillis%2CtotalDurationMillis%2CskipCount%2CfailCount%2CtotalCount%2CpassCount%5D%5D%2ClastCompletedBuild%5BfullName%2Cnumber%2Ctimestamp%2Cduration%2Cactions%5BqueuingDurationMillis%2CtotalDurationMillis%2CskipCount%2CfailCount%2CtotalCount%2CpassCount%5D%5D%2ClastFailedBuild%5BfullName%2Cnumber%2Ctimestamp%2Cduration%2Cactions%5BqueuingDurationMillis%2CtotalDurationMillis%2CskipCount%2CfailCount%2CtotalCount%2CpassCount%5D%5D%2ClastStableBuild%5BfullName%2Cnumber%2Ctimestamp%2Cduration%2Cactions%5BqueuingDurationMillis%2CtotalDurationMillis%2CskipCount%2CfailCount%2CtotalCount%2CpassCount%5D%5D%2ClastSuccessfulBuild%5BfullName%2Cnumber%2Ctimestamp%2Cduration%2Cactions%5BqueuingDurationMillis%2CtotalDurationMillis%2CskipCount%2CfailCount%2CtotalCount%2CpassCount%5D%5D%2ClastUnstableBuild%5BfullName%2Cnumber%2Ctimestamp%2Cduration%2Cactions%5BqueuingDurationMillis%2CtotalDurationMillis%2CskipCount%2CfailCount%2CtotalCount%2CpassCount%5D%5D%2ClastUnsuccessfulBuild%5BfullName%2Cnumber%2Ctimestamp%2Cduration%2Cactions%5BqueuingDurationMillis%2CtotalDurationMillis%2CskipCount%2CfailCount%2CtotalCount%2CpassCount%5D%5D%5D (Caused by SSLError(SSLError(1, u'[SSL: UNKNOWN_PROTOCOL] unknown protocol (_ssl.c:618)'),))

Python version: 2.7.5
System: centos 7
Jenkins Version: 2.121.3
requests version: 2.18.4
prometheus-client version: 0.6.0