Exec<| tag == 'python-virtualenv' |> changes and breaks the API

[ilyash]

commit 55b942d added
Exec<| tag == 'python-virtualenv' |> ->

It breaks beaver module because it can no longer

python::virtualenv { $venv:
  ...
  require => Class['python'],
}

It causes circular dependency. Class['python'] depends on all virtualenvs but beaver needs Class['python'] for it's virtualenv.

See https://github.com/evenup/evenup-beaver/blob/1cf0be3a6595fde59ba54231cacbd4c7d142b24b/manifests/package.pp#L37

[ilyash]

Thanks!