After changeset http://hg.python.org/lookup/dbed7cacfb7e, calling the crawl_delay method for a robots.txt files that has a crawl-delay for * useragents always returns None.

Ex:

Python 3.6.0a0 (default:1aae9b6a6929+, Oct  9 2015, 22:08:05)
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import urllib.robotparser
>>> parser = urllib.robotparser.RobotFileParser()
>>> parser.set_url('https://www.carthage.edu/robots.txt')
>>> parser.read()
>>> parser.crawl_delay('test_robotparser')
>>> parser.crawl_delay('*')
>>> print(parser.default_entry.delay)
120
>>>

Excerpt from https://www.carthage.edu/robots.txt:

User-agent: *
Crawl-Delay: 120
Disallow: /cgi-bin

I have written a patch that solves this. With patch, output is:

Python 3.6.0a0 (default:1aae9b6a6929+, Oct  9 2015, 22:08:05)
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import urllib.robotparser
>>> parser = urllib.robotparser.RobotFileParser()
>>> parser.set_url('https://www.carthage.edu/robots.txt')
>>> parser.read()
>>> parser.crawl_delay('test_robotparser')
120
>>> parser.crawl_delay('*')
120
>>> print(parser.default_entry.delay)
120
>>>

This also applies to the request_rate method.