anchor.diff:              for p in g.Value.NugetPackages do
                   let k = g.Key,p.Name
                   if usedPackages.ContainsKey k then
  -                    failwithf "Package %O is referenced more than once in %s (group %O)" p.Name referencesFile.FileName g.Key
  +                    failwithf "Package %O is referenced more than once in %s within group %O." p.Name referencesFile.FileName g.Key
                   usedPackages.Add(k,p)
   
           for g in referencesFile.Groups do
  
positive.code:             for p in g.NugetPackages do
                  let k = groupName,p.Name
                  if usedPackages.ContainsKey k then
                      failwithf "Package %O is referenced more than once in %s (group %O)" p.Name referencesFile.FileName groupName
                  usedPackages.Add(k,p)
  
              g.NugetPackages
  
negative.code:     /// Creates a paket.lock file at given location
      static member Create (lockFileName: string, installOptions: InstallOptions, resolvedPackages: PackageResolver.Resolution, resolvedSourceFiles: ModuleResolver.ResolvedSourceFile list) : LockFile =
          let resolvedPackages = resolvedPackages.GetModelOrFail()
          let mainGroup = 
              { Name = Constants.MainDependencyGroup
                Options = installOptions
                Resolution = resolvedPackages
                RemoteFiles = resolvedSourceFiles }
  
          let groups = [Constants.MainDependencyGroup, mainGroup] |> Map.ofSeq
          let lockFile = LockFile(lockFileName, groups)
          lockFile.Save()
  