EXM 3.1 for Sitecore CMS 8.0 Update-3 Upgrade Note

Recently Sitecore relase a new version of Email Experience Manager - EXM 3.1 rev. 150703 for Sitecore 8.0 rev. 150427

This EXM version includes drastic changes from its earlier version, like moving dispatch queue into SQL database instead of MongoDB, etc

I tried to upgrade from 3.0 to 3.1 and the process went smoothly except in one occation.

When tried to run the Update Installation Wizard with the EXM 3.1 Update file (Email Experience Manager 3.1 rev. 150703.update), at the end of the installation process, it returned a critical error stating a .js file deletion failed error.

But, I later found in the upgrade documentation (EXM 31 Update Instructions.pdf) that, they are asking to manually deleting this file and its containing folder.

Remove the following files from all instances of EXM :
sitecore\shell\client\Applications\ECM\EmailCampaign.Client\Pipelines\UpdateMessagevariant\UpdateVariant.js
sitecore\shell\client\Applications\ECM\EmailCampaign.Client\Pipelines\UpdateMessagevariant