The assembly has been renamed. Change on the CodeTaskFactory MSBuild Task the AssemblyFile parameter to…(in your error there should be a targets file name where this task resides)
AssemblyFile="C:\Program Files (x86)\MSBuild\14.0\Bin\Microsoft.Build.Tasks.Core.dll"
Chances are someone tried to be clever and use an MSBuild property like this..(which doesn’t work for MSBuild 14 but would for 12)…
AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.v$(MSBuildToolsVersion).dll"
Just fyi…There are some others as well such as Microsoft.Build.Utilities.v12.0.dll has been renamed to Microsoft.Build.Utilities.Core.dll