Auto merge of #1678 - chris-morgan:master, r=alexcrichton
Auto merge of #1678 - chris-morgan:master, r=alexcrichton

This regression, introduced in d3f590f59ff72f1d3b457ed3716483ce472053c6 in #1674, caused `make` to fail on machines where `python` is Python 3 rather than Python 2, because `dict.keys()` returns a set-like object that does not support indexing rather than a list.

`date = next(iter(snaps.keys()))` would be an adequate fix too, but I’m not particularly happy with either of them, for neither would stand up to the removal of the `break` statement: one is inadequate because dictionaries are unordered collections, the other is inadequate because `current` would refer to the *last* rather than the *first* snapshot in the file.

nipunn1313/cargo,rust-lang/cargo,Gankro/cargo,Gankro/cargo,pcwalton/cargo,Frederick888/cargo,nipunn1313/cargo,apjanke/cargo,gchp/cargo,Turbo87/cargo,Kimundi/cargo,akiss77/cargo,eerden/cargo,blaenk/cargo,youprofit/cargo,winger/cargo,nipunn1313/cargo,JacobHenner/cargo,vyskocilm/cargo,cesarb/cargo,JacobHenner/cargo,Gankro/cargo,mark-buer/cargo,cmr/cargo,Frederick888/cargo,liigo/cargo,shaleh/cargo,iliekturtles/cargo,AndiDog/cargo,liigo/cargo,JacobHenner/cargo,vi/cargo,beni55/cargo,ArtemGr/cargo,ArtemGr/cargo,achanda/cargo,felixbuenemann/cargo,huonw/cargo,rustyhorde/cargo,winger/cargo,shaleh/cargo,mceier/cargo,youprofit/cargo,Ticki/cargo,frewsxcv/cargo,eerden/cargo,vi/cargo,Gankro/cargo,gchp/cargo,beni55/cargo,Dineshs91/cargo,mneumann/cargo,worr/cargo,worr/cargo,vyskocilm/cargo,frewsxcv/cargo,johshoff/cargo,huonw/cargo,JacobHenner/cargo,AndiDog/cargo,ThinTim/cargo,Turbo87/cargo,Ticki/cargo,rust-lang/cargo,tshepang/cargo,gchp/cargo,Kimundi/cargo,nipunn1313/cargo,tafia/cargo,felixbuenemann/cargo,durka/cargo,ArtemGr/cargo,tshepang/cargo,mneumann/cargo,cesarb/cargo,ThinTim/cargo,apjanke/cargo,gchp/cargo,blaenk/cargo,eerden/cargo,rust-lang/cargo,pcwalton/cargo,ucarion/cargo,cmr/cargo,ucarion/cargo,tsurai/cargo,achanda/cargo,mceier/cargo,Turbo87/cargo,pcwalton/cargo,youprofit/cargo,blaenk/cargo,fhahn/cargo,ucarion/cargo,vojtechkral/cargo,aturon/cargo,winger/cargo,eminence/cargo,Ticki/cargo,tafia/cargo,iliekturtles/cargo,huonw/cargo,tafia/cargo,pcwalton/cargo,tsurai/cargo,mark-buer/cargo,winger/cargo,mark-buer/cargo,tshepang/cargo,johshoff/cargo,tsurai/cargo,mark-buer/cargo,apjanke/cargo,ThinTim/cargo,blaenk/cargo,gchp/cargo,ArtemGr/cargo,beni55/cargo,vojtechkral/cargo,mneumann/cargo,alex/cargo,ThinTim/cargo,brson/cargo,shaleh/cargo,brson/cargo,alex/cargo,Frederick888/cargo,youprofit/cargo,vyskocilm/cargo,durka/cargo,fhahn/cargo,rustyhorde/cargo,akiss77/cargo,alex/cargo,tsurai/cargo,JacobHenner/cargo,shaleh/cargo,ArtemGr/cargo,Kimundi/cargo,aturon/cargo,frewsxcv/cargo,Turbo87/cargo,alex/cargo,felixbuenemann/cargo,mark-buer/cargo,tsurai/cargo,youprofit/cargo,Dineshs91/cargo,mceier/cargo,vyskocilm/cargo,ThinTim/cargo,shaleh/cargo,iliekturtles/cargo,cesarb/cargo,liigo/cargo,frewsxcv/cargo,fhahn/cargo,liigo/cargo,Gankro/cargo,aturon/cargo,apjanke/cargo,AndiDog/cargo,AndiDog/cargo,Kimundi/cargo,beni55/cargo,liigo/cargo,worr/cargo,beni55/cargo,Frederick888/cargo,sbeckeriv/cargo,cesarb/cargo,vojtechkral/cargo,johshoff/cargo,cmr/cargo,brson/cargo,akiss77/cargo,mneumann/cargo,eerden/cargo,vi/cargo,akiss77/cargo,eminence/cargo,apjanke/cargo,durka/cargo,Dineshs91/cargo,sbeckeriv/cargo,rustyhorde/cargo,sbeckeriv/cargo,johshoff/cargo,Dineshs91/cargo,rust-lang/cargo,cesarb/cargo,huonw/cargo,fhahn/cargo,felixbuenemann/cargo,brson/cargo,worr/cargo,johshoff/cargo,Dineshs91/cargo,vi/cargo,mceier/cargo,frewsxcv/cargo,aturon/cargo,brson/cargo,fhahn/cargo,tafia/cargo,Frederick888/cargo,Kimundi/cargo,tshepang/cargo,akiss77/cargo,AndiDog/cargo,iliekturtles/cargo,mceier/cargo,eminence/cargo,vi/cargo,Turbo87/cargo,sbeckeriv/cargo,blaenk/cargo,aturon/cargo,ucarion/cargo,durka/cargo,vojtechkral/cargo,tafia/cargo,cmr/cargo,iliekturtles/cargo,Ticki/cargo,ucarion/cargo,rustyhorde/cargo,eminence/cargo,huonw/cargo,Ticki/cargo,achanda/cargo,eerden/cargo,vyskocilm/cargo,worr/cargo,winger/cargo,mneumann/cargo,achanda/cargo,felixbuenemann/cargo,pcwalton/cargo,alex/cargo,cmr/cargo