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error MSB4014: The build stopped unexpectedly because of an internal failure.
Microsoft.Build.Exceptions.BuildAbortedException: Build was canceled. MSBuild.exe could not be launched as a child node as it could not be found at the location "C:\Windows\Microsoft.NET\Framework\v4.0.30319\MSBuild.exe". If necessary, specify the correct location in the BuildParameters, or with the MSBUILD_EXE_PATH environment variable.
   en Microsoft.Build.BackEnd.NodeManager.AttemptCreateNode(INodeProvider nodeProvider, NodeConfiguration nodeConfiguration)
   en Microsoft.Build.BackEnd.NodeManager.CreateNode(NodeConfiguration configuration, NodeAffinity nodeAffinity)
   en Microsoft.Build.Execution.BuildManager.PerformSchedulingActions(IEnumerable`1 responses)
   en Microsoft.Build.Execution.BuildManager.HandleNewRequest(Int32 node, BuildRequestBlocker blocker)
   en Microsoft.Build.Execution.BuildManager.IssueRequestToScheduler(BuildSubmission submission, Boolean allowMainThreadBuild, BuildRequestBlocker blocker)      

Que no puede encontrar MSBuild.exe donde lo has especificado...Ya existe hotfix para eso, está aquí: https://connect.microsoft.com/VisualStudio/Downloads/DownloadDetails.aspx?DownloadID=31354