checkbox failed to build, cannot import pkg_resources

Checkbox-dev daily failed to build with the following error message:

[checkbox/parsers/tests/test_submission.py]
Traceback (most recent call last):
  File "./test", line 211, in <module>
    main()
  File "./test", line 207, in main
    sys.exit(runner_func(opts))
  File "./test", line 137, in test_with_unittest
    module = __import__(modpath, None, None, [""])
  File "/build/buildd/checkbox-0.14.10+bzr1769+201210131625~quantal1/checkbox/parsers/tests/test_submission.py", line 25, in <module>
    from checkbox.parsers.submission import SubmissionParser
  File "/build/buildd/checkbox-0.14.10+bzr1769+201210131625~quantal1/checkbox/parsers/submission.py", line 26, in <module>
    from pkg_resources import resource_string
ImportError: No module named pkg_resources

The debian/control file probably needs a new dependency on python3-pkg-resources to build the source package.