I believe the proper form of this try/except (and the other nearly identical try/excepts) is:

```python
try:
    pgcursor.execute(sql, sql_args)
except PostgresError, e:
    self._connection.rollback()
    raise QiitaDBExecutionError("Error running SQL query: %s", e)
else:
    result = pgcursor.fetchone()
```

This logic could be generalized for all the ``execute*`` methods with:

```python
def _execute_and_result(self, cursor, sql, sql_args, fetch=None):
    fetches = {'fetchall': lambda x: x.fetchall(), 'fetchone': lambda x: x.fetchone()}
    fetch_f = fetches.get(fetch, lambda x: None)

    try:
        cursor.execute(sql, sql_args)
    except PostgresError, e:
        self._connection.rollback()
        raise QiitaDBExecutionError("Error running SQL query: %s", e)
    else:
        result = fetch_f(cursor)
    return result
```