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If you've built Platform Plugins based on the older version of Dojo that we used to ship, you'll have to migrate your code to work with the new AMD loader syntax. The Dojo foundation has a very comprehensive guide on how to migrate from the old Dojo syntax and loader and syntax to AMD here: Dojo 2.0 Migration.
Note: You do not have to include dojo.js in your page as described in their migration guide. We use the RequireJS loader instead which is available on any page which includes the webcontext.js script. AMD Javascript Modules (RequireJS)#webcontext
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