Enum describing possible campaign feed errors.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v23/errors/campaign_feed_error.proto)

| Enums ||
|---|---|
| ## `CANNOT_CREATE_ALREADY_EXISTING_CAMPAIGN_FEED` | The CampaignFeed already exists. UPDATE should be used to modify the existing CampaignFeed. |
| ## `CANNOT_CREATE_FOR_REMOVED_FEED` | The specified feed is removed. |
| ## `CANNOT_MODIFY_REMOVED_CAMPAIGN_FEED` | Cannot update removed campaign feed. |
| ## `FEED_ALREADY_EXISTS_FOR_PLACEHOLDER_TYPE` | An active feed already exists for this campaign and placeholder type. |
| ## `INVALID_PLACEHOLDER_TYPE` | Invalid placeholder type. |
| ## `LEGACY_FEED_TYPE_READ_ONLY` | Feed is read only. |
| ## `MISSING_FEEDMAPPING_FOR_PLACEHOLDER_TYPE` | Feed mapping for this placeholder type does not exist. |
| ## `NO_EXISTING_LOCATION_CUSTOMER_FEED` | Location CampaignFeeds cannot be created unless there is a location CustomerFeed for the specified feed. |
| ## `UNKNOWN` | The received error code is not known in this version. |
| ## `UNSPECIFIED` | Enum unspecified. |