This error message occurs when you are using Visual Studio 2012 to deploy an app to a SharePoint 2013 under the following circumstances

• The site you are using is a host-named site collection that is not the root site collection for the web application AND
• the site is not a developer site

To avoid this error message, you can either

• deploy to the root site collection of the web application (and not the host-named site collection) – which is not a valid choice sometimes
  or

• Enable the "Developer Site" Feature in your target site by executing the following PowerShell command: Enable-SPFeature -Identity e374875e-06b6-11e0-b0fa-57f5dfd72085 -url

  or

• Enable the “App Sideloading” Feature in your target site:
  Enable-SPFeature -Identity AE3A1339-61F5-4f8f-81A7-ABD2DA956A7D –url <siteurl> or

• Deploy to a developer site (which has the features already enabled)

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