[1.6.x] Added link to LogRecord attributes in logging.txt

Ultimately, a log record needs to be rendered as text. Formatters

describe the exact format of that text. A formatter usually consists

of a Python formatting string; however, you can also write custom

formatters to implement specific formatting behavior.

of a Python formatting string containing

:ref:`LogRecord attributes <python:logrecord-attributes>`; however,

you can also write custom formatters to implement specific formatting behavior.

Using logging

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