I'm not completely sure it covers your certificate use case, but since it took me some time to find out, I still want to share this snipped that retrieves the email address for a given user name in Python without special Jenkins libraries. It uses an API token and "supports" (actually ignores) https:
def _get_email_adress(user):
request = urllib.request.Request("https://jenkins_server/user/"+ user +"/api/json")
#according to https://stackoverflow.com/a/28052583/4609258 the following is ugly
context = ssl._create_unverified_context()
base64string = base64.b64encode(bytes('%s:%s' % ('my user name', 'my API token'),'ascii'))
request.add_header("Authorization", "Basic %s" % base64string.decode('utf-8'))
with urllib.request.urlopen(request, context=context) as url:
user_data = json.loads(url.read().decode())
for property in user_data['property']:
if property["_class"]=="hudson.tasks.Mailer$UserProperty":
return property["address"];