“Unknown Error” when launching Visual Studio 2017 Community after installation

remove this folder (or similar):

%LocalAppData%\Microsoft\VisualStudio\15.0_db2a872f

• folder name 15.0_db2a872f could be different in your machine eg. 15.0_XXXXXXX
• found in the vs startup log that processing of Progression_NativePackage_Component_x86.pkgdef bailed out, indicating an inconsistent extension installation