[coqdep] clean up error handling for coqdep
[coqdep] clean up error handling for coqdep

Zimmi48/coq,ejgallego/coq,SkySkimmer/coq,SkySkimmer/coq,SkySkimmer/coq,Zimmi48/coq,SkySkimmer/coq,Zimmi48/coq,coq/coq,coq/coq,coq/coq,ejgallego/coq,Zimmi48/coq,coq/coq,ejgallego/coq,ejgallego/coq