Unable to add paket folder to solution #214

$ mono buildsupport/paket.exe convert-from-nuget --force --verbose
[snip]
Paket failed with:
   Unable to add paket folder to solution backend/src/Backend.sln

StackTrace:
    at <StartupCode$paket>.$SolutionFile+AddPaketFolder@46-1.Invoke (System.String message) [0x00000] in <filename unknown>:0
  at Microsoft.FSharp.Core.PrintfModule+PrintFormatToStringThen@575-3[Microsoft.FSharp.Core.Unit].Invoke (Microsoft.FSharp.Core.Unit unitVar0) [0x00000] in <filename unknown>:0
  at Microsoft.FSharp.Core.PrintfImpl.go@523-3[Unit,String,Unit] (System.String fmt, Int32 len, Microsoft.FSharp.Core.FSharpFunc`2 outputChar, Microsoft.FSharp.Core.FSharpFunc`2 outa, Microsoft.FSharp.Core.Unit os, Microsoft.FSharp.Core.FSharpFunc`2 finalize, Microsoft.FSharp.Collections.FSharpList`1 args, Int32 i) [0x00000] in <filename unknown>:0
  at Microsoft.FSharp.Core.PrintfImpl.run@521[Unit,String,Unit] (Microsoft.FSharp.Core.FSharpFunc`2 initialize, System.String fmt, Int32 len, Microsoft.FSharp.Collections.FSharpList`1 args) [0x00000] in <filename unknown>:0
  at Microsoft.FSharp.Core.PrintfImpl.capture@540[Unit,String,Unit] (Microsoft.FSharp.Core.FSharpFunc`2 initialize, System.String fmt, Int32 len, Microsoft.FSharp.Collections.FSharpList`1 args, System.Type ty, Int32 i) [0x00000] in <filename unknown>:0
  at Microsoft.FSharp.Core.PrintfImpl+capture@540-1[Microsoft.FSharp.Core.Unit,System.String,Microsoft.FSharp.Core.Unit].Invoke (Microsoft.FSharp.Collections.FSharpList`1 args, System.Type ty, Int32 i) [0x00000] in <filename unknown>:0
  at Microsoft.FSharp.Core.FSharpFunc`2[Microsoft.FSharp.Collections.FSharpList`1[System.Object],System.Type].InvokeFast[Int32,Object] (Microsoft.FSharp.Core.FSharpFunc`2 func, Microsoft.FSharp.Collections.FSharpList`1 arg1, System.Type arg2, Int32 arg3) [0x00000] in <filename unknown>:0
  at Microsoft.FSharp.Core.FSharpFunc`2[System.Type,System.Object].InvokeFast[Object] (Microsoft.FSharp.Core.FSharpFunc`2 func, System.Type arg1, System.Object arg2) [0x00000] in <filename unknown>:0
  at Microsoft.FSharp.Core.PrintfImpl+buildFunctionForOneArgPat@212.Invoke (System.Object inp) [0x00000] in <filename unknown>:0
  at <StartupCode$FSharp-Core>.$Reflect+Invoke@720-4[System.String,Microsoft.FSharp.Core.Unit].Invoke (System.String inp) [0x00000] in <filename unknown>:0
  at Paket.SolutionFile.AddPaketFolder (System.String dependenciesFile, Microsoft.FSharp.Core.FSharpOption`1 lockFile) [0x00000] in <filename unknown>:0
  at Paket.NuGetConvert.ConvertFromNuget (Boolean force, Boolean installAfter, Boolean initAutoRestore, System.String dependenciesFileName) [0x00000] in <filename unknown>:0
  at Paket.Program+clo@95-2.Invoke (Microsoft.FSharp.Core.Unit unitVar) [0x00000] in <filename unknown>:0
  at <StartupCode$paket>.$Paket.Program.main@ () [0x00000] in <filename unknown>:0