WMF 5.1 Release Notes: https://msdn.microsoft.com/en-us/powershell/wmf/5.1/release-notes

 2017.05.10 
   WMF Version: 5.1.14409.1005
   Pkg Version: 5.1.14409.20170510
   - fix to .NET version checking logic for Win7 / Server 2008 R2

 2017.04.02 
   WMF Version: 5.1.14409.1005
   Pkg Version: 5.1.14409.20170402
   - powershell install log files are serialized so that they don't accumulate in the same file across multiple attempts
   - if an errors occurs, the errors are extracted from the log file and displayed into the chocolatey log

 2017.03.01 
   WMF Version: 5.1.14409.1005
   Pkg Version: 5.1.14409.20170301
   - fixed bug misidentifying the .net version on Server 2012

 2017.02.14 
   WMF Version: 5.1.14409.1005
   Pkg Version: 5.1.14409.20170214
   - fixed bug causing Server 2012 (non-R2) from being detected as windows 8

  2017.01.26  (5.1.14409.1005)
    -  New: Installs WMF 5.1
    -  Tested On: Win7 + PSH 2, Win7 + WMF 3, Win 8.1 + WMF 4, 2012 R2 + WMF 5.0, Windows 10
    -  EXPERIMENTAL: Attempts to Preserve the PSModulePath when WMF 5.1 is 
                     installed over WMF 3 on Windows 7 or Server 2008.

         How the experimental support works:
           *) It only takes effect on Windows 7 and Server 2008 R2 and only if WMF 3 is installed
           *) You must pre-install at least .NET 4.5.1 (required by WMF 4 and later)
           *) You must use the -force switch on the package

           What steps are taken to preserve PSModulePath:
              1) The custom parts of the PSModulePath backed up to BackupPSModulePath
              2) A fix up script that appends those values to the PSModulePath is written to:
                       %WINDIR%\Temp\psmodulepathfixup.ps1
              3) A scheduled task is setup for the next reboot that runs the fix up script

           If you find that #3 does not work correctly, then you can use #1 or #2 with some of your 
           own automation to recover from the PsModulePath overwrite.

  2016.12.01  (5.0.10586.20170115)
    -  Fixed: Package generates error that you must upgrade to Windows 8.1 on Server 2012 (not-R2) domain controllers.

  2016.12.01  (5.0.10586.20161201)
    -  IMPORTANT: This package no longer updates a machine to an older version of PowerShell when 5 cannot be applied, the package must
         be explicitly called with the -version parameter if the system being configured cannot take PowerShell 5.
    -  Updated to use checksums
    -  Updated to use re-released MSUs discussed here (old ones getting 404s):
         https://blogs.msdn.microsoft.com/powershell/2016/02/24/windows-management-framework-wmf-5-0-rtm-packages-has-been-republished/
    -  Checks and errors if Windows Update service is disabled, the error message suggests enabling it just for the time this package runs
         (it is a common good practice to disable Windows Update when doing long running orchestration,
         however, it must be enabled for this package to run)

TROUBLESHOOTING GUIDANCE:
  If you receive the error 'ERROR: Running ["C:\Windows\System32\wusa.exe" ' it generally means the system does not have the prerequisites 
  required by the .MSU file.  
  
  Find the reference to the the log file "PowerShell.Install.evtx" and double-click it to open it in eventvwr.  The reason for the failure
  should be within the messages in this file.

  Please do this before reporting the error because it will be the first thing you are asked to do in order to establish root cause.