10 files declare their use of FieldException in Drupal 8

BaseFieldOverride.php in core/lib/Drupal/Core/Field/Entity/BaseFieldOverride.php

EntityDefinitionUpdateTest.php in core/tests/Drupal/KernelTests/Core/Entity/EntityDefinitionUpdateTest.php

field.purge.inc in core/modules/field/field.purge.inc

Provides support for field data purge after mass deletion.

FieldConfig.php in core/modules/field/src/Entity/FieldConfig.php

FieldCrudTest.php in core/modules/field/tests/src/Kernel/FieldCrudTest.php

FieldStorageConfig.php in core/modules/field/src/Entity/FieldStorageConfig.php

FieldStorageConfigEntityUnitTest.php in core/modules/field/tests/src/Unit/FieldStorageConfigEntityUnitTest.php

Contains \Drupal\Tests\field\Unit\FieldStorageConfigEntityUnitTest.

FieldStorageConfigUpdateForbiddenException.php in core/modules/field/src/FieldStorageConfigUpdateForbiddenException.php

FieldStorageCrudTest.php in core/modules/field/tests/src/Kernel/FieldStorageCrudTest.php

SqlContentEntityStorageSchema.php in core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorageSchema.php