我有 vagrant 1.7.2 并且我需要 vagrant-vsphere 插件但是当我尝试命令时：vagrant pluging install vagrant-vpshere显示这些错误消息：
Installing the 'vagrant-vsphere' plugin. This can take a few minutes...
Fetching source index from http://gems.hashicorp.com/
Fetching gem metadata from https://rubygems.org/.........
Fetching additional metadata from https://rubygems.org/..........
Resolving dependencies...
Using builder 3.2.2
Using gyoku 1.2.2
Using mini_portile 0.6.0
Using nokogiri 1.6.3.1
Using akami 1.2.2
Using bundler 1.7.11
Using hitimes 1.2.2
Using timers 4.0.1
Using celluloid 0.16.0
Using ffi 1.9.10
Using childprocess 0.5.8
Using erubis 2.7.0
Using gssapi 1.0.3
Using hashicorp-checkpoint 0.1.4
Using httpclient 2.6.0.1
Using rack 1.6.0
Using httpi 0.9.7
Using i18n 0.6.11
Using rb-fsevent 0.9.4
Using rb-inotify 0.9.5
Using listen 2.8.4
Using little-plugger 1.1.4
Using log4r 1.1.10
Using multi_json 1.11.2
Using logging 1.8.2
Using mime-types 1.25.1
Using net-ssh 2.9.2
Using net-scp 1.1.2
Using net-sftp 2.1.2
Using nori 1.1.5
Using rb-kqueue 0.2.3
Using trollop 2.1.2
Using rbvmomi 1.8.2
Using rest-client 1.6.9
Using rubyntlm 0.1.1
Using wasabi 1.0.0
Using savon 0.9.5
Using uuidtools 2.1.5
Using wdm 0.1.0
Using winrm 1.1.3
Using vagrant 1.7.2
NoMethodError: undefined method `size' for nil:NilClass
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:
An error occurred while installing vagrant-share (1.1.4), and Bundler cannot continue.
Make sure that `gem install vagrant-share -v '1.1.4'` succeeds before bundling.
在这些错误之后，我手动安装了 gem vagrant-share 1.1.4 但我发现 vagrant 有插件 vagrant-share 1.1.3 作为系统插件：
# vagrant plugin update vagrant-share
vagrant-share (1.1.3, system)
问题：如何以与 vagrant 1.7.x 一致的方式安装 vagrant-sphere 插件？