Entity Info Storage
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Problem
Entity information is not stored persistently anywhere. The information is parsed from hooks (hook_entity_info() and hook_entity_info_alter()) and temporary cached. It's true that Drupal stores entity info in the field_bundle_settings_ENTITYTYPE__BUNDLENAME variables (see https://drupal.org/node/1569594) but those variables are only inserted/changed via UI and for this reason we cannot rely on them.
This will make almost impossible to upgrade to Drupal 8 using the new "migration in core" system. All pieces, like view modes or others, that are stored along with entity info, cannot be evaluated as sources for D7 to D8 migration.
Solution
The module stores the entity information into system variables. The migration manager should visit the admin/config/system/entity_info on D7 site prior running the migration. In this way the migration will be provided with reasonable source data.