create branch 2.6

--HG--
branch : 2.6
Don't fail if effort is None

issue3725
review4271003
(grafted from 44849f9370494038173cff188e0d1191401d5cb4)

--HG--
branch : 2.6
extra : source : 44849f9370494038173cff188e0d1191401d5cb4