Fix #56: exception if file specified in cookiefile option does not exist
Fix #56: exception if file specified in cookiefile option does not exist

kevinlondon/grab,raybuhr/grab,giserh/grab,shaunstanislaus/grab,istinspring/grab,shaunstanislaus/grab,liorvh/grab,DDShadoww/grab,maurobaraldi/grab,maurobaraldi/grab,lorien/grab,lorien/grab,huiyi1990/grab,alihalabyah/grab,giserh/grab,codevlabs/grab,SpaceAppsXploration/grab,kevinlondon/grab,liorvh/grab,raybuhr/grab,SpaceAppsXploration/grab,istinspring/grab,pombredanne/grab-1,pombredanne/grab-1,alihalabyah/grab,codevlabs/grab,huiyi1990/grab,DDShadoww/grab