Error for installing vagrant-unison plugin

gistfile1.txt

[user@computer ~]$ vagrant plugin install vagrant-unison
Installing the 'vagrant-unison' plugin. This can take a few minutes...
/usr/share/gems/gems/psych-3.1.0/lib/psych.rb:237: warning: already initialized constant Psych::LIBYAML_VERSION
/usr/share/ruby/psych.rb:237: warning: previous definition of LIBYAML_VERSION was here
/usr/share/gems/gems/psych-3.1.0/lib/psych.rb:239: warning: already initialized constant Psych::NOT_GIVEN
/usr/share/ruby/psych.rb:239: warning: previous definition of NOT_GIVEN was here

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 listen (~> 0.7.3) and listen (= 3.1.5)
  Activated listen-3.1.5
  which does not match conflicting dependency (~> 0.7.3)

  Conflicting dependency chains:
    listen (= 3.1.5), 3.1.5 activated

  versus:
    vagrant-unison (> 0), 0.0.5 activated, depends on
    listen (~> 0.7.3)