(Wangle) Catch all exceptions in `then() -> Future`
(Wangle) Catch all exceptions in `then() -> Future`

Summary: Saw this while debugging some stuff. Just an oversight, right?

Test Plan: Ran all the tests.

Reviewed By: hans@fb.com

Subscribers: folly-diffs@, jsedgwick, yfeldblum

FB internal diff: D1843016

Signature: t1:1843016:1423704557:d9fdb4b879ab4fcfda54a5fcb16a639df15872b5

cole14/folly,PoisonBOx/folly,clearlinux/folly,kernelim/folly,clearlylin/folly,project-zerus/folly,rklabs/folly,raphaelamorim/folly,Hincoin/folly,Hincoin/folly,tomhughes/folly,Eagle-X/folly,brunomorishita/folly,sonnyhu/folly,PPC64/folly,stonegithubs/folly,CJstar/folly,lifei/folly,bobegir/folly,zhiweicai/folly,bikong2/folly,yangjin-unique/folly,facebook/folly,KSreeHarsha/folly,rklabs/folly,charsyam/folly,bowlofstew/folly,alexst07/folly,ykarlsbrun/folly,alexst07/folly,gaoyingie/folly,stonegithubs/folly,bowlofstew/folly,yangjin-unique/folly,clearlylin/folly,fw1121/folly,kernelim/folly,ykarlsbrun/folly,shaobz/folly,bsampath/folly,cppfool/folly,loverszhaokai/folly,sakishum/folly,project-zerus/folly,floxard/folly,bsampath/folly,arg0/folly,clearlylin/folly,raphaelamorim/folly,clearlinux/folly,nickhen/folly,constantine001/folly,zhiweicai/folly,bikong2/folly,gaoyingie/folly,zhiweicai/folly,leolujuyi/folly,arg0/folly,wildinto/folly,kernelim/folly,cppfool/folly,wildinto/folly,cppfool/folly,hongliangzhao/folly,loverszhaokai/folly,guker/folly,colemancda/folly,constantine001/folly,bikong2/folly,loversInJapan/folly,cppfool/folly,gavioto/folly,chjp2046/folly,project-zerus/folly,bowlofstew/folly,PoisonBOx/folly,mqeizi/folly,clearlinux/folly,upsoft/folly,charsyam/folly,CJstar/folly,hongliangzhao/folly,xzmagic/folly,cole14/folly,floxard/folly,alexst07/folly,renyinew/folly,hongliangzhao/folly,bsampath/folly,bobegir/folly,guker/folly,SammyK/folly,lifei/folly,guker/folly,gavioto/folly,cole14/folly,fw1121/folly,SammyK/folly,upsoft/folly,colemancda/folly,KSreeHarsha/folly,chjp2046/folly,sonnyhu/folly,arg0/folly,yangjin-unique/folly,romange/folly,renyinew/folly,tempbottle/folly,Orvid/folly,doctaweeks/folly,sonnyhu/folly,loverszhaokai/folly,bobegir/folly,renyinew/folly,Orvid/folly,facebook/folly,brunomorishita/folly,project-zerus/folly,mqeizi/folly,shaobz/folly,kernelim/folly,upsoft/folly,guker/folly,project-zerus/folly,juniway/folly,gaoyingie/folly,Orvid/folly,reddit/folly,bikong2/folly,romange/folly,zhiweicai/folly,clearlylin/folly,brunomorishita/folly,colemancda/folly,alexst07/folly,wildinto/folly,fw1121/folly,alexst07/folly,reddit/folly,bsampath/folly,nickhen/folly,PoisonBOx/folly,theiver9827/folly,theiver9827/folly,reddit/folly,floxard/folly,facebook/folly,Eagle-X/folly,clearlinux/folly,Orvid/folly,KSreeHarsha/folly,renyinew/folly,facebook/folly,guker/folly,gavioto/folly,bikong2/folly,upsoft/folly,SammyK/folly,SeanRBurton/folly,charsyam/folly,Eagle-X/folly,zhiweicai/folly,renyinew/folly,leolujuyi/folly,CJstar/folly,rklabs/folly,raphaelamorim/folly,yangjin-unique/folly,arg0/folly,hongliangzhao/folly,SeanRBurton/folly,Hincoin/folly,reddit/folly,shaobz/folly,stonegithubs/folly,tempbottle/folly,kernelim/folly,loverszhaokai/folly,juniway/folly,colemancda/folly,brunomorishita/folly,Hincoin/folly,cole14/folly,sakishum/folly,PPC64/folly,raphaelamorim/folly,xzmagic/folly,PPC64/folly,doctaweeks/folly,raphaelamorim/folly,yangjin-unique/folly,loversInJapan/folly,leolujuyi/folly,tempbottle/folly,fw1121/folly,nickhen/folly,lifei/folly,sonnyhu/folly,gavioto/folly,ykarlsbrun/folly,Eagle-X/folly,chjp2046/folly,sakishum/folly,tempbottle/folly,tempbottle/folly,nickhen/folly,hongliangzhao/folly,fw1121/folly,wildinto/folly,doctaweeks/folly,lifei/folly,sonnyhu/folly,romange/folly,bowlofstew/folly,juniway/folly,ykarlsbrun/folly,bobegir/folly,cole14/folly,leolujuyi/folly,charsyam/folly,tomhughes/folly,tomhughes/folly,bsampath/folly,constantine001/folly,bobegir/folly,SeanRBurton/folly,juniway/folly,PoisonBOx/folly,theiver9827/folly,xzmagic/folly,sakishum/folly,leolujuyi/folly,sakishum/folly,gaoyingie/folly,ykarlsbrun/folly,KSreeHarsha/folly,tomhughes/folly,arg0/folly,cppfool/folly,CJstar/folly,clearlinux/folly,loversInJapan/folly,nickhen/folly,CJstar/folly,SammyK/folly,Eagle-X/folly,SammyK/folly,PPC64/folly,juniway/folly,wildinto/folly,facebook/folly,lifei/folly,clearlylin/folly,loversInJapan/folly,floxard/folly,chjp2046/folly,mqeizi/folly,mqeizi/folly,loverszhaokai/folly,Orvid/folly,rklabs/folly,stonegithubs/folly,gavioto/folly,colemancda/folly,rklabs/folly,chjp2046/folly,xzmagic/folly,reddit/folly,PoisonBOx/folly,shaobz/folly,constantine001/folly,theiver9827/folly,gaoyingie/folly,mqeizi/folly,brunomorishita/folly,upsoft/folly,bowlofstew/folly,SeanRBurton/folly,romange/folly,loversInJapan/folly,tomhughes/folly,KSreeHarsha/folly,stonegithubs/folly,doctaweeks/folly,xzmagic/folly,floxard/folly,shaobz/folly,doctaweeks/folly,constantine001/folly,PPC64/folly,SeanRBurton/folly,Hincoin/folly,theiver9827/folly,romange/folly