Failed to initialize the PowerShell host.If your PowerShell execution policy setting is set to AllSigned, open the PackageManagerConsole to initialize the host first
Open Windows PowerShell, run as Administrator
Setting an execution policy to RemoteSigned or Unrestricted should work. It must be changed under an administrator mode via a PowerShell console. Be aware that changes will be applied according to the bit version of the PowerShell console, so 32bit or 64 bit. So if you want to install a package in Visual Studio (32 bit version) which requires a specific policy you should change settings of the policy via PowerShell (x86).
The command in PowerShell (as administrator) to set the policy to unrestricted (as noted by @Gabriel in the comments) is:
Windows® 7 中包含 Windows PowerShell 2.0。 它还包含可以添加到 Windows PowerShell 的其他 cmdlet、提供程序和工具，以便您可以使用和管理其他 Windows 技术，如 Active Directory(R) 域服务、Windows® BitLocker™ 驱动器加密、DHCP 服务器服务、组策略、远程桌面服务和 Windows Server Backup。