nice error for Restart outside a proof (Close: #4235)
nice error for Restart outside a proof (Close: #4235)

ale-f/coq,silene/coq,william-lawvere/coq,JasonGross/coq,william-lawvere/coq,jpdeplaix/coq,Lionel-Rieg/coq,gmalecha/coq,Matafou/coq,jpdeplaix/coq,ejgallego/coq,maximedenes/coq,ejgallego/coq,ejgallego/coq,Zimmi48/coq,TheTypoMaster/coq,gares/coq,letouzey/coq-wip,SkySkimmer/coq,asr/coq,JasonGross/coq,barras/coq,Ptival/coq,herbelin/github-coq,letouzey/coq-wip,coq/coq,mlasson/coq,coq/coq,asr/coq,letouzey/coq-wip,TOSPIO/coq,amintimany/coq,mattam82/coq,maximedenes/coq,Ptival/coq,TOSPIO/coq,Lionel-Rieg/coq,ejgallego/coq,mlasson/coq,SkySkimmer/coq,Matafou/coq,letouzey/coq-wip,amintimany/coq,gares/coq,silene/coq,maximedenes/coq,SkySkimmer/coq,ppedrot/coq,jpdeplaix/coq,gares/coq,Lionel-Rieg/coq,JasonGross/coq,asr/coq,barras/coq,mlasson/coq,Zimmi48/coq,SkySkimmer/coq,ale-f/coq,amintimany/coq,letouzey/coq-wip,mattam82/coq,coq/coq,gmalecha/coq,ppedrot/coq,herbelin/github-coq,ppedrot/coq,barras/coq,Zimmi48/coq,8l/coq,Matafou/coq,william-lawvere/coq,gares/coq,maximedenes/coq,TheTypoMaster/coq,gmalecha/coq,Zimmi48/coq,JasonGross/coq,herbelin/github-coq,ppedrot/coq,ppedrot/coq,ale-f/coq,maximedenes/coq,TheTypoMaster/coq,mattam82/coq,8l/coq,gares/coq,coq/coq,silene/coq,8l/coq,TOSPIO/coq,Ptival/coq