"vagrant plugin install vagrant-scp" fails

To reproduce:

$ sudo apt install vagrant virtualbox
$ vagrant box add ubuntu/xenial64
$ vagrant plugin install vagrant-scp
Installing the 'vagrant-scp' plugin. This can take a few minutes...
Bundler, the underlying system Vagrant uses to install plugins,
reported an error. The error is shown below. These errors are usually
caused by misconfigured plugin installations or transient network
issues. The error from Bundler is:

conflicting dependencies fog-core (~> 1.43.0) and fog-core (= 1.45.0)
  Activated fog-core-1.45.0
  which does not match conflicting dependency (~> 1.43.0)

  Conflicting dependency chains:
    fog-core (= 1.45.0), 1.45.0 activated

  versus:
    vagrant-libvirt (> 0), 0.0.41 activated, depends on
    fog-core (~> 1.43.0)

(don't know if the 'box add' is required)

This was reported earlier at
https://github.com/dotless-de/vagrant-vbguest/issues/292
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=896904
https://tutorials.technology/solved_errors/Vagrant-plugin-install--conflicting-dependencies-fog-core--~%3E-1_43_0--and-fog-core----1_45_0-.html

In all three cases, the workaround was 'install vagrant 2.0.3 from vendor'.

And indeed, installing 2.0.4 from vendor solved the problem.

So... please update!
They're up to 2.1.5 now, dunno whether latest 2.0.x or 2.1.x is appropriate.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: vagrant 2.0.2+dfsg-2ubuntu8
ProcVersionSignature: User Name 4.15.0-36.39-generic 4.15.18
Uname: Linux 4.15.0-36-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
Date: Thu Oct 4 19:13:52 2018
PackageArchitecture: all
SourcePackage: vagrant
UpgradeStatus: No upgrade log present (probably fresh install)