Add unittest for save_certificate
Add unittest for save_certificate

sjerdo/letsencrypt,luorenjin/letsencrypt,tyagi-prashant/letsencrypt,DavidGarciaCat/letsencrypt,riseofthetigers/letsencrypt,lbeltrame/letsencrypt,lmcro/letsencrypt,Hasimir/letsencrypt,goofwear/letsencrypt,piru/letsencrypt,kuba/letsencrypt,riseofthetigers/letsencrypt,twstrike/le_for_patching,DavidGarciaCat/letsencrypt,jsha/letsencrypt,hsduk/lets-encrypt-preview,beermix/letsencrypt,fmarier/letsencrypt,sjerdo/letsencrypt,Sveder/letsencrypt,mitnk/letsencrypt,wteiken/letsencrypt,ghyde/letsencrypt,brentdax/letsencrypt,thanatos/lets-encrypt-preview,lbeltrame/letsencrypt,mitnk/letsencrypt,martindale/letsencrypt,deserted/letsencrypt,skynet/letsencrypt,xgin/letsencrypt,TheBoegl/letsencrypt,stweil/letsencrypt,mrb/letsencrypt,BillKeenan/lets-encrypt-preview,Bachmann1234/letsencrypt,armersong/letsencrypt,martindale/letsencrypt,letsencrypt/letsencrypt,mrb/letsencrypt,jsha/letsencrypt,jtl999/certbot,kevinlondon/letsencrypt,luorenjin/letsencrypt,BillKeenan/lets-encrypt-preview,beermix/letsencrypt,brentdax/letsencrypt,bsmr-misc-forks/letsencrypt,Sveder/letsencrypt,TheBoegl/letsencrypt,rlustin/letsencrypt,Jadaw1n/letsencrypt,thanatos/lets-encrypt-preview,BKreisel/letsencrypt,armersong/letsencrypt,jtl999/certbot,rlustin/letsencrypt,kuba/letsencrypt,dietsche/letsencrypt,tyagi-prashant/letsencrypt,piru/letsencrypt,goofwear/letsencrypt,wteiken/letsencrypt,stweil/letsencrypt,bsmr-misc-forks/letsencrypt,VladimirTyrin/letsencrypt,Jadaw1n/letsencrypt,kevinlondon/letsencrypt,skynet/letsencrypt,hsduk/lets-encrypt-preview,dietsche/letsencrypt,VladimirTyrin/letsencrypt,fmarier/letsencrypt,BKreisel/letsencrypt,ghyde/letsencrypt,lmcro/letsencrypt,g1franc/lets-encrypt-preview,letsencrypt/letsencrypt,Bachmann1234/letsencrypt,deserted/letsencrypt,xgin/letsencrypt,g1franc/lets-encrypt-preview,Hasimir/letsencrypt,twstrike/le_for_patching