Civicrm Integration: Error while adding api function
This looks like your CiviCRM install has an extension enabled in the DB which is not present, or was moved, on your disk.

Perhaps the extension you're working on was renamed after first being enabled, perhaps other changes were made to info.xml or the core extension files, perhaps it was moved, or perhaps your DB had another extension enabled on the remote server which isn't present locally.

The CiviCRM extensions page might be informative to check, otherwise you can compare extensions listed in the database to the ones which are available locally.