Spider not found appears when crawling with Scrapy

I ran into a mysterious error when I was about to crawl with Scrapy, so I made a note of it.

Status

Execute the following from the command prompt scrapy crawl websiteCrawl.py

raise KeyError("Spider not found: {}".format(spider_name))
KeyError: 'Spider not found: websiteCrawl.py'

Error is output. I haven't set anything strange, but what does it mean that there is no Spider?

Correspondence

If you remove .py and execute it, no error will occur. scrapy crawl websiteCrawl

It was a pitiful careless mistake, but if you save it as a tab, it will be .py, so I wonder if it is easy to make this kind of error.