vagrant 1.7.4
Host: OS X 10.10.4
Guest: Windows 10 build 10162
This works using a Windows 8.1 guest.
Line of interest
/opt/vagrant/embedded/gems/gems/winrm-fs-0.2.0/lib/winrm-fs/core/command_executor.rb:59:in `assert_command_success': uninitialized constant WinRM::FS::Core::CommandExecutor::WinRMUploadError (NameError)
Debug output: https://gist.github.com/dafyddj/f347cb99034786f2d282
This is resolved in my comment with a patch in #6060
Fixed by #6060