[issue35922] robotparser crawl_delay and request_rate do not work with no matching entry

[Joseph Myers]

New submission from Joseph Myers <jsm at polyomino.org.uk>:

RobotFileParser.crawl_delay and RobotFileParser.request_rate raise AttributeError for a robots.txt with no matching entry for the given user-agent, including no default entry, rather than returning None which would be correct according to the documentation.  E.g.:

>>> from urllib.robotparser import RobotFileParser
>>> parser = RobotFileParser()
>>> parser.parse([])
>>> parser.crawl_delay('example')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.6/urllib/robotparser.py", line 182, in crawl_delay
    return self.default_entry.delay
AttributeError: 'NoneType' object has no attribute 'delay'

----------
components: Library (Lib)
messages: 334982
nosy: joseph_myers
priority: normal
severity: normal
status: open
title: robotparser crawl_delay and request_rate do not work with no matching entry
type: behavior
versions: Python 3.6, Python 3.7, Python 3.8

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35922>
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