Visual Studio 2017 publishing .net core mvc app errors with 'the command "dotnet bundle" exited with code 1'

Question

I've just migrated a .net core MVC project which was working fine and publishing fine in Visual Studio 2015 to Visual Studio 2017. Problem is that I cannot publish the app at all, I just get a publish failure and the error 'the command "dotnet bundle" exited with code 1'

I've found a few post on other sites and stackoverflow but they all suggest adding this to the .csproj file (see this post here)

<ItemGroup>
   <DotNetCliToolReference Include="BundlerMinifier.Core" Version="2.4.337"/>
</ItemGroup>

But despite adding this I still get the same error!?!

I can't seem to find anything else to try... don't suppose anyone has anymore or any other suggestions I've missed?

P.S. Not loving Microsoft's backward step (imho) from project.json files to the old XML style .csproj files!