Error after upgrade - missing file

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Core Version - 5.7.5.9
Version Installed - 5.7.5.6

After starting an upgrade, I get the following error, and cannot complete the upgrade.

Doctrine\Common\Proxy\AbstractProxyFactory::getProxyDefinition(): Failed opening required '/home/sitename/public_html/application/config/doctrine/proxies/__CG__ConcreteCoreFileStorageLocationStorageLocation.php' (include_path='/home/sitename/public_html/concrete/vendor:.:/usr/lib/php:/usr/local/lib/php:/usr/local/php55/lib/php')

The file referenced, "__CG__ConcreteCoreFileStorageLocationStorageLocation.php" is not at the location specified.

jgaryt