[docs] [issue35781] `logger.warn` method is used in "Logging HOWTO" documentation though `logger.warn` method is deprecated in Python 3.7

[yuji38kwmt]

New submission from yuji38kwmt <yuji38kwmt at gmail.com>:

### Target Documentation

https://docs.python.org/3/howto/logging.html#configuring-logging


### Actual Sample Code

```
# 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warn('warn message')
logger.error('error message')
logger.critical('critical message')
```

### Expected Sample Code

```
# 'application' code
logger.debug('debug message')
logger.info('info message')
logger.warning('warn message')
logger.error('error message')
logger.critical('critical message')
```

### Reference

> There is an obsolete method warn which is functionally identical to warning. As warn is deprecated, please do not use it - use warning instead.

https://docs.python.org/3.7/library/logging.html#logging.Logger.warning

----------
assignee: docs at python
components: Documentation
messages: 334030
nosy: docs at python, yuji38kwmt
priority: normal
severity: normal
status: open
title: `logger.warn` method is used in "Logging HOWTO" documentation though `logger.warn` method is deprecated in Python 3.7
type: behavior
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35781>
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