Make sure that thunks are restored properly if an exception occurs
Make sure that thunks are restored properly if an exception occurs

Fixes Hydra bug #67.

zimbatm/nix,dezgeg/nix,ttuegel/nix,bjornfor/nix,NixOS/nix,shlevy/nix,shlevy/nix,dezgeg/nix,bennofs/nix,dezgeg/nix,ysangkok/nix,vcunat/nix,ehmry/nix,jcumming/nix,gebner/nix,puffnfresh/nix,edolstra/nix,peti/nix,peti/nix,bennofs/nix,edolstra/nix,vcunat/nix,garbas/nix,tchajed/nix,peti/nix,ttuegel/nix,vizanto/nix,layus/nix,dtzWill/nix,jcumming/nix,bjornfor/nix,edolstra/nix,ysangkok/nix,aucampia/nix,garbas/nix,rycee/nix,NixOS/nix,shlevy/nix,wmertens/nix,joelmo/nix,dezgeg/nix,shlevy/nix,jcumming/nix,ehmry/nix,gridaphobe/nix,rowhit/nix,jcumming/nix,ehmry/nix,rycee/nix,tchajed/nix,offlinehacker/nix,vcunat/nix,acowley/nix,ehmry/nix,joelmo/nix,puffnfresh/nix,zimbatm/nix,NixOS/nix,dtzWill/nix,gridaphobe/nix,bennofs/nix,dtzWill/nix,wmertens/nix,pikajude/nix,bjornfor/nix,rowhit/nix,rycee/nix,garbas/nix,gridaphobe/nix,vizanto/nix,ehmry/nix,edolstra/nix,acowley/nix,garbas/nix,ehmry/nix,dtzWill/nix,peti/nix,nbp/nix,aucampia/nix,rowhit/nix,bjornfor/nix,wmertens/nix,rowhit/nix,ysangkok/nix,rycee/nix,offlinehacker/nix,gridaphobe/nix,puffnfresh/nix,NixOS/nix,pikajude/nix,aucampia/nix,ttuegel/nix,peti/nix,zimbatm/nix,layus/nix,edolstra/nix,layus/nix,bennofs/nix,nbp/nix,tchajed/nix,pikajude/nix,gebner/nix,tchajed/nix,ttuegel/nix,offlinehacker/nix,gebner/nix,shlevy/nix,joelmo/nix,wmertens/nix,zimbatm/nix,nbp/nix,layus/nix,offlinehacker/nix,nbp/nix,vcunat/nix,rycee/nix,aucampia/nix,vizanto/nix,dtzWill/nix,puffnfresh/nix,acowley/nix,acowley/nix,layus/nix,joelmo/nix,dezgeg/nix,vizanto/nix,gebner/nix,NixOS/nix,garbas/nix