travis-ci: add production Python 3 test suite.
travis-ci: add production Python 3 test suite.

- Add production testing to .travis.yml file for PY3 env

Fixes #1710.

mahim97/zulip,amyliu345/zulip,ryanbackman/zulip,cosmicAsymmetry/zulip,paxapy/zulip,punchagan/zulip,SmartPeople/zulip,zulip/zulip,vaidap/zulip,peguin40/zulip,verma-varsha/zulip,vabs22/zulip,AZtheAsian/zulip,eeshangarg/zulip,vaidap/zulip,SmartPeople/zulip,amanharitsh123/zulip,Galexrt/zulip,synicalsyntax/zulip,sonali0901/zulip,hackerkid/zulip,aakash-cr7/zulip,tommyip/zulip,sonali0901/zulip,synicalsyntax/zulip,timabbott/zulip,hackerkid/zulip,Juanvulcano/zulip,amanharitsh123/zulip,Diptanshu8/zulip,blaze225/zulip,kou/zulip,dattatreya303/zulip,rishig/zulip,sharmaeklavya2/zulip,aakash-cr7/zulip,brainwane/zulip,calvinleenyc/zulip,timabbott/zulip,Jianchun1/zulip,AZtheAsian/zulip,sup95/zulip,Galexrt/zulip,paxapy/zulip,joyhchen/zulip,vabs22/zulip,JPJPJPOPOP/zulip,KingxBanana/zulip,jainayush975/zulip,reyha/zulip,souravbadami/zulip,zacps/zulip,dattatreya303/zulip,andersk/zulip,aakash-cr7/zulip,showell/zulip,Jianchun1/zulip,KingxBanana/zulip,andersk/zulip,dattatreya303/zulip,dattatreya303/zulip,grave-w-grave/zulip,jainayush975/zulip,punchagan/zulip,calvinleenyc/zulip,umkay/zulip,JPJPJPOPOP/zulip,eeshangarg/zulip,KingxBanana/zulip,JPJPJPOPOP/zulip,PhilSk/zulip,rht/zulip,rishig/zulip,susansls/zulip,blaze225/zulip,mahim97/zulip,calvinleenyc/zulip,jrowan/zulip,punchagan/zulip,vaidap/zulip,KingxBanana/zulip,kou/zulip,isht3/zulip,cosmicAsymmetry/zulip,zacps/zulip,joyhchen/zulip,amyliu345/zulip,hackerkid/zulip,hackerkid/zulip,jackrzhang/zulip,rishig/zulip,dawran6/zulip,amanharitsh123/zulip,AZtheAsian/zulip,peguin40/zulip,eeshangarg/zulip,umkay/zulip,niftynei/zulip,jackrzhang/zulip,Galexrt/zulip,dhcrzf/zulip,joyhchen/zulip,timabbott/zulip,punchagan/zulip,arpith/zulip,vabs22/zulip,vabs22/zulip,zacps/zulip,souravbadami/zulip,tommyip/zulip,Jianchun1/zulip,blaze225/zulip,dawran6/zulip,joyhchen/zulip,kou/zulip,christi3k/zulip,souravbadami/zulip,andersk/zulip,ryanbackman/zulip,SmartPeople/zulip,zulip/zulip,brockwhittaker/zulip,timabbott/zulip,amyliu345/zulip,Jianchun1/zulip,jackrzhang/zulip,showell/zulip,showell/zulip,mohsenSy/zulip,shubhamdhama/zulip,shubhamdhama/zulip,christi3k/zulip,andersk/zulip,niftynei/zulip,mahim97/zulip,synicalsyntax/zulip,AZtheAsian/zulip,Jianchun1/zulip,jphilipsen05/zulip,AZtheAsian/zulip,amyliu345/zulip,grave-w-grave/zulip,Diptanshu8/zulip,shubhamdhama/zulip,tommyip/zulip,jrowan/zulip,brainwane/zulip,SmartPeople/zulip,vaidap/zulip,timabbott/zulip,shubhamdhama/zulip,verma-varsha/zulip,dhcrzf/zulip,SmartPeople/zulip,niftynei/zulip,brainwane/zulip,hackerkid/zulip,christi3k/zulip,blaze225/zulip,sup95/zulip,jphilipsen05/zulip,samatdav/zulip,andersk/zulip,sup95/zulip,arpith/zulip,amyliu345/zulip,isht3/zulip,zacps/zulip,TigorC/zulip,paxapy/zulip,grave-w-grave/zulip,brockwhittaker/zulip,susansls/zulip,synicalsyntax/zulip,umkay/zulip,showell/zulip,dattatreya303/zulip,shubhamdhama/zulip,jrowan/zulip,jrowan/zulip,j831/zulip,arpith/zulip,vabs22/zulip,christi3k/zulip,susansls/zulip,shubhamdhama/zulip,peguin40/zulip,cosmicAsymmetry/zulip,jackrzhang/zulip,vikas-parashar/zulip,reyha/zulip,mohsenSy/zulip,kou/zulip,niftynei/zulip,grave-w-grave/zulip,SmartPeople/zulip,isht3/zulip,vikas-parashar/zulip,eeshangarg/zulip,brockwhittaker/zulip,amanharitsh123/zulip,dhcrzf/zulip,blaze225/zulip,jrowan/zulip,peguin40/zulip,j831/zulip,sharmaeklavya2/zulip,paxapy/zulip,PhilSk/zulip,mohsenSy/zulip,Galexrt/zulip,rht/zulip,eeshangarg/zulip,amyliu345/zulip,hackerkid/zulip,umkay/zulip,isht3/zulip,ryanbackman/zulip,punchagan/zulip,rishig/zulip,rht/zulip,PhilSk/zulip,Juanvulcano/zulip,rishig/zulip,souravbadami/zulip,sup95/zulip,reyha/zulip,andersk/zulip,calvinleenyc/zulip,souravbadami/zulip,cosmicAsymmetry/zulip,paxapy/zulip,amanharitsh123/zulip,mohsenSy/zulip,Juanvulcano/zulip,andersk/zulip,Galexrt/zulip,cosmicAsymmetry/zulip,amanharitsh123/zulip,TigorC/zulip,sonali0901/zulip,umkay/zulip,arpith/zulip,j831/zulip,tommyip/zulip,jainayush975/zulip,showell/zulip,timabbott/zulip,punchagan/zulip,AZtheAsian/zulip,zulip/zulip,sonali0901/zulip,JPJPJPOPOP/zulip,jphilipsen05/zulip,sup95/zulip,punchagan/zulip,eeshangarg/zulip,jackrzhang/zulip,PhilSk/zulip,jphilipsen05/zulip,zulip/zulip,Diptanshu8/zulip,vaidap/zulip,dawran6/zulip,christi3k/zulip,synicalsyntax/zulip,Juanvulcano/zulip,jrowan/zulip,Juanvulcano/zulip,dhcrzf/zulip,showell/zulip,arpith/zulip,zulip/zulip,zulip/zulip,rishig/zulip,jackrzhang/zulip,jphilipsen05/zulip,zulip/zulip,vaidap/zulip,calvinleenyc/zulip,vabs22/zulip,niftynei/zulip,niftynei/zulip,reyha/zulip,reyha/zulip,zacps/zulip,samatdav/zulip,shubhamdhama/zulip,susansls/zulip,mohsenSy/zulip,TigorC/zulip,aakash-cr7/zulip,KingxBanana/zulip,samatdav/zulip,peguin40/zulip,timabbott/zulip,rishig/zulip,rht/zulip,brockwhittaker/zulip,verma-varsha/zulip,grave-w-grave/zulip,sharmaeklavya2/zulip,jainayush975/zulip,jainayush975/zulip,mahim97/zulip,reyha/zulip,sup95/zulip,aakash-cr7/zulip,mohsenSy/zulip,souravbadami/zulip,susansls/zulip,Diptanshu8/zulip,tommyip/zulip,zacps/zulip,j831/zulip,tommyip/zulip,sonali0901/zulip,brockwhittaker/zulip,verma-varsha/zulip,joyhchen/zulip,dhcrzf/zulip,umkay/zulip,kou/zulip,susansls/zulip,TigorC/zulip,mahim97/zulip,jphilipsen05/zulip,sonali0901/zulip,j831/zulip,synicalsyntax/zulip,eeshangarg/zulip,blaze225/zulip,synicalsyntax/zulip,tommyip/zulip,kou/zulip,brainwane/zulip,brainwane/zulip,dhcrzf/zulip,kou/zulip,jackrzhang/zulip,Galexrt/zulip,ryanbackman/zulip,rht/zulip,isht3/zulip,ryanbackman/zulip,vikas-parashar/zulip,mahim97/zulip,KingxBanana/zulip,samatdav/zulip,PhilSk/zulip,JPJPJPOPOP/zulip,grave-w-grave/zulip,dawran6/zulip,Jianchun1/zulip,j831/zulip,vikas-parashar/zulip,verma-varsha/zulip,arpith/zulip,christi3k/zulip,rht/zulip,paxapy/zulip,sharmaeklavya2/zulip,Diptanshu8/zulip,peguin40/zulip,calvinleenyc/zulip,PhilSk/zulip,verma-varsha/zulip,isht3/zulip,brockwhittaker/zulip,TigorC/zulip,cosmicAsymmetry/zulip,Juanvulcano/zulip,Diptanshu8/zulip,samatdav/zulip,Galexrt/zulip,TigorC/zulip,vikas-parashar/zulip,jainayush975/zulip,umkay/zulip,rht/zulip,samatdav/zulip,vikas-parashar/zulip,brainwane/zulip,JPJPJPOPOP/zulip,dawran6/zulip,sharmaeklavya2/zulip,showell/zulip,aakash-cr7/zulip,hackerkid/zulip,ryanbackman/zulip,dattatreya303/zulip,joyhchen/zulip,sharmaeklavya2/zulip,dhcrzf/zulip,brainwane/zulip,dawran6/zulip