I'm getting:
exceptions.TypeError: not all arguments converted during string formatting
from this:
cursor.execute("SELECT * FROM `item` WHERE `url` = %s", (urljoin( base_url, item_url ) ))
Syntax seems fine - any ideas?
The issue here is you are passing in a string, where you should be passing in a tuple. Note the extra comma at the end:
execute("SELECT * FROM `item` WHERE `url` = %s", (urljoin(base_url, item_url),))