py26reqs.txt needs to be path-relative
py26reqs.txt needs to be path-relative

Fixes: #1630

bsmr-misc-forks/letsencrypt,jtl999/certbot,mrb/letsencrypt,kuba/letsencrypt,wteiken/letsencrypt,twstrike/le_for_patching,VladimirTyrin/letsencrypt,Sveder/letsencrypt,Sveder/letsencrypt,lbeltrame/letsencrypt,jsha/letsencrypt,letsencrypt/letsencrypt,martindale/letsencrypt,DavidGarciaCat/letsencrypt,letsencrypt/letsencrypt,brentdax/letsencrypt,brentdax/letsencrypt,xgin/letsencrypt,mitnk/letsencrypt,TheBoegl/letsencrypt,lmcro/letsencrypt,goofwear/letsencrypt,lbeltrame/letsencrypt,piru/letsencrypt,kuba/letsencrypt,martindale/letsencrypt,bsmr-misc-forks/letsencrypt,thanatos/lets-encrypt-preview,dietsche/letsencrypt,xgin/letsencrypt,TheBoegl/letsencrypt,twstrike/le_for_patching,stweil/letsencrypt,lmcro/letsencrypt,dietsche/letsencrypt,jtl999/certbot,VladimirTyrin/letsencrypt,thanatos/lets-encrypt-preview,DavidGarciaCat/letsencrypt,piru/letsencrypt,goofwear/letsencrypt,mitnk/letsencrypt,stweil/letsencrypt,mrb/letsencrypt,wteiken/letsencrypt,jsha/letsencrypt