PDOException: SQLSTATE[42S02]: Base table or view not found:

The tip from comment #10 worked for me, but after the upgrade (via the Durpal UI) I still get a failure because update 7301 failed at the rename of the flags table, but succeeded with the rename of the `flag_content` table. Since the whole update needs to be repeated, it's now failing at the rename of the `flag_content` table.

Failed: DatabaseSchemaObjectExistsException: Cannot rename flag_content to flagging: table flagging already exists. in DatabaseSchema_mysql->renameTable() (line 320 of /var/www/html/docroot/includes/database/mysql/schema.inc).

I also made the following changes to `flag_update_7301()`:

function flag_update_7301() {
  if (db_table_exists('flag_content')) {
    if (!db_table_exists('flagging')) {
      db_rename_table('flag_content', 'flagging');
    }
    else {
      db_drop_table('flag_content');
    }
  }
  if (db_table_exists('flags')) {
    db_rename_table('flags', 'flag');
  }
  // A second cache clear appears to be required here...
  cache_clear_all();
  // ...which in fact isn't enough, as the schema cache appears to need explicit
  // clearing to prevent the next updates failing to get the schema for the new
  // table names.
  drupal_get_schema(NULL, TRUE);
}