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##### SUMMARY
<!--- Describe the new feature/improvement briefly below -->
New Percona/MySQL 8 privileges with underscore is not working. 
the following error is coming 

`MSG: invalid privileges string: Invalid privileges specified: frozenset({'BACKUP_ADMIN'})`

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
mysql_user module
most likely the new privileges needs to be added to lib/ansible/modules/database/mysql/mysql_user.py

##### ADDITIONAL INFORMATION
<!--- Describe how the feature would be used, why it is needed and what it would solve -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

<!--- HINT: You can also paste gist.github.com links for larger files -->

output[pieces[0]] = re.split(r',\s*(?=[^)]*(?:\(|$))', pieces[1].upper())
            for i in output[pieces[0]]:
                privs.append(re.sub(r'\s*\(.*\)', '', i))
        else:
            output[pieces[0]] = pieces[1].upper().split(',')
            privs = output[pieces[0]]
        new_privs = frozenset(privs)
        if not new_privs.issubset(VALID_PRIVS):
            raise InvalidPrivsError('Invalid privileges specified: %s' % new_privs.difference(VALID_PRIVS))
    if '*.*' not in output:
        output['*.*'] = ['USAGE']
    
    
    if 'REQUIRESSL' in priv and not set(output['*.*']).difference(set(['GRANT', 'REQUIRESSL'])):
        output['*.*'].append('USAGE')
    return output
def privileges_revoke(cursor, user, host, db_table, priv, grant_option):
    
    db_table = db_table.replace('%', '%%')
    if grant_option:
        query = ["REVOKE GRANT OPTION ON %s" % db_table]
        query.append("FROM %s@%s")
        query = ' '.join(query)
        cursor.execute(query, (user, host))
    priv_string = ",".join([p for p in priv if p not in ('GRANT', 'REQUIRESSL')])
    query = ["REVOKE %s ON %s" % (priv_string, db_table)]
    query.append("FROM %s@%s")
    query = ' '.join(query)
    cursor.execute(query, (user, host))
def privileges_grant(cursor, user, host, db_table, priv):