Import symbol urlparse from package urllib.parse

[slaufmann]

This fixes a regression introduced by the last commit (#6961ae14a2980162db37e0563c096414245fa356)

The regression shows itself by the following error message when running crawler.py:

Traceback (most recent call last):                 
  File "crawler.py", line 460, in <module>         
    sys.exit(main(args))                           
  File "crawler.py", line 271, in main             
    site.check(include_known=options.include_known)
  File "crawler.py", line 137, in check            
    if not urlparse(match_url).scheme:             
NameError: name 'urlparse' is not defined          

[grandchild]

Thank you! I missed this.