I have amended the code based on solutions offered below by the great folks here; I get the error shown below the code here.
from scrapy.spider import BaseSp
From Scrapy docs:
def parse(self, response): # ... code ommited next_page = response.urljoin(next_page) yield scrapy.Request(next_page, self.parse)
that is, response object has a method to do exactly this.
response