Drop ancient Python 2.3 support which used deprecated unittest apis.
Drop ancient Python 2.3 support which used deprecated unittest apis.

sorenh/pyopenssl,reaperhulk/pyopenssl,r0ro/pyopenssl,adamwolf/pyopenssl,samv/pyopenssl,aalba6675/pyopenssl,Lukasa/pyopenssl,alex/pyopenssl,r0ro/pyopenssl,mitghi/pyopenssl,Lukasa/pyopenssl,pyca/pyopenssl,mhils/pyopenssl,rackerlabs/pyopenssl,lvh/pyopenssl,daodaoliang/pyopenssl,mschmo/pyopenssl,JensTimmerman/pyopenssl,aalba6675/pyopenssl,kjav/pyopenssl,JensTimmerman/pyopenssl,kediacorporation/pyopenssl,mhils/pyopenssl,alex/pyopenssl,mitghi/pyopenssl,lvh/pyopenssl,elitest/pyopenssl,kediacorporation/pyopenssl,reaperhulk/pyopenssl,hynek/pyopenssl,sholsapp/pyopenssl,rackerlabs/pyopenssl,hynek/pyopenssl