Revert "Upgrade to celery 3.x. (bug 823510)" ... for science!
Revert "Upgrade to celery 3.x. (bug 823510)" ... for science!

This reverts commit b4c410f8097ea45800be0ba80b36224eb1cb8d55.

mstriemer/addons-server,wagnerand/olympia,harry-7/addons-server,mdaif/olympia,SuriyaaKudoIsc/olympia,shahbaz17/zamboni,wagnerand/addons-server,Prashant-Surya/addons-server,atiqueahmedziad/addons-server,mudithkr/zamboni,yfdyh000/olympia,andymckay/zamboni,muffinresearch/addons-server,Revanth47/addons-server,Witia1/olympia,eviljeff/olympia,wagnerand/zamboni,johancz/olympia,andymckay/zamboni,aviarypl/mozilla-l10n-addons-server,harry-7/addons-server,diox/zamboni,tsl143/zamboni,mrrrgn/olympia,mozilla/zamboni,Witia1/olympia,koehlermichael/olympia,Joergen/olympia,wagnerand/zamboni,bqbn/addons-server,jpetto/olympia,beni55/olympia,Nolski/olympia,crdoconnor/olympia,Revanth47/addons-server,koehlermichael/olympia,spasovski/zamboni,aviarypl/mozilla-l10n-addons-server,Nolski/olympia,mudithkr/zamboni,mozilla/zamboni,diox/olympia,spasovski/zamboni,mstriemer/addons-server,Nolski/olympia,robhudson/zamboni,tsl143/addons-server,elysium001/zamboni,ddurst/zamboni,Joergen/olympia,beni55/olympia,muffinresearch/addons-server,Revanth47/addons-server,yfdyh000/olympia,ingenioustechie/zamboni,anaran/olympia,clouserw/zamboni,elysium001/zamboni,eviljeff/olympia,tsl143/addons-server,Joergen/zamboni,mstriemer/zamboni,eviljeff/zamboni,koehlermichael/olympia,eviljeff/olympia,bqbn/addons-server,muffinresearch/olympia,mozilla/addons-server,eviljeff/olympia,tsl143/addons-server,tsl143/addons-server,andymckay/olympia,jasonthomas/zamboni,diox/zamboni,mrrrgn/olympia,Witia1/olympia,spasovski/zamboni,Hitechverma/zamboni,harikishen/addons-server,ddurst/zamboni,muffinresearch/olympia,mstriemer/olympia,aviarypl/mozilla-l10n-addons-server,ngokevin/zamboni,mstriemer/addons-server,andymckay/addons-server,atiqueahmedziad/addons-server,magopian/olympia,crdoconnor/olympia,clouserw/zamboni,luckylavish/zamboni,andymckay/zamboni,kumar303/addons-server,mozilla/olympia,Jobava/zamboni,Joergen/olympia,wagnerand/olympia,ingenioustechie/zamboni,diox/olympia,kumar303/zamboni,magopian/olympia,anaran/olympia,muffinresearch/olympia,jasonthomas/zamboni,tsl143/zamboni,harry-7/addons-server,tsl143/zamboni,ingenioustechie/zamboni,jpetto/olympia,spasovski/zamboni,beni55/olympia,harikishen/addons-server,Witia1/olympia,kmaglione/olympia,yfdyh000/olympia,lavish205/olympia,kmaglione/olympia,diox/zamboni,Joergen/olympia,tsl143/zamboni,mozilla/olympia,lavish205/olympia,bqbn/addons-server,harry-7/addons-server,yfdyh000/olympia,jasonthomas/zamboni,anaran/olympia,mstriemer/olympia,jamesthechamp/zamboni,psiinon/addons-server,johancz/olympia,Joergen/zamboni,anaran/olympia,Nolski/olympia,Jobava/zamboni,mudithkr/zamboni,lavish205/olympia,mozilla/addons-server,psiinon/addons-server,wagnerand/addons-server,kmaglione/olympia,mdaif/olympia,muffinresearch/addons-server,robhudson/zamboni,mstriemer/olympia,Nolski/olympia,wagnerand/olympia,Jobava/zamboni,aviarypl/mozilla-l10n-addons-server,kmaglione/olympia,kmaglione/olympia,eviljeff/zamboni,wagnerand/addons-server,washort/zamboni,beni55/olympia,luckylavish/zamboni,eviljeff/zamboni,kumar303/olympia,Joergen/zamboni,Prashant-Surya/addons-server,mstriemer/addons-server,harikishen/addons-server,mdaif/olympia,washort/zamboni,magopian/olympia,kumar303/addons-server,jasonthomas/zamboni,wagnerand/zamboni,mdaif/olympia,koehlermichael/olympia,luckylavish/zamboni,diox/zamboni,diox/olympia,Joergen/zamboni,robhudson/zamboni,jamesthechamp/zamboni,andymckay/addons-server,ayushagrawal288/zamboni,mozilla/olympia,elysium001/zamboni,ayushagrawal288/zamboni,magopian/olympia,jamesthechamp/zamboni,Jobava/zamboni,mozilla/addons-server,beni55/olympia,johancz/olympia,mstriemer/zamboni,ngokevin/zamboni,mudithkr/zamboni,washort/zamboni,atiqueahmedziad/addons-server,jpetto/olympia,mrrrgn/olympia,shahbaz17/zamboni,Joergen/zamboni,andymckay/olympia,psiinon/addons-server,kumar303/olympia,SuriyaaKudoIsc/olympia,mozilla/zamboni,yfdyh000/olympia,elysium001/zamboni,kumar303/olympia,jpetto/olympia,Joergen/olympia,wagnerand/zamboni,mozilla/olympia,SuriyaaKudoIsc/olympia,atiqueahmedziad/addons-server,Hitechverma/zamboni,bqbn/addons-server,kumar303/olympia,mstriemer/olympia,wagnerand/olympia,wagnerand/addons-server,Hitechverma/zamboni,robhudson/zamboni,Hitechverma/zamboni,Witia1/olympia,harikishen/addons-server,crdoconnor/olympia,ayushagrawal288/zamboni,eviljeff/zamboni,Prashant-Surya/addons-server,lavish205/olympia,Revanth47/addons-server,jamesthechamp/zamboni,crdoconnor/olympia,koehlermichael/olympia,ayushagrawal288/zamboni,kumar303/zamboni,ingenioustechie/zamboni,clouserw/zamboni,washort/zamboni,ddurst/zamboni,shahbaz17/zamboni,andymckay/addons-server,mozilla/addons-server,muffinresearch/addons-server,luckylavish/zamboni,andymckay/olympia,kumar303/zamboni,psiinon/addons-server,mrrrgn/olympia,johancz/olympia,ngokevin/zamboni,mstriemer/zamboni,shahbaz17/zamboni,andymckay/olympia,SuriyaaKudoIsc/olympia,andymckay/addons-server,crdoconnor/olympia,kumar303/addons-server,Joergen/zamboni,muffinresearch/olympia,Prashant-Surya/addons-server,muffinresearch/olympia,mrrrgn/olympia,muffinresearch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