Sorry, forgot to include the output of doctest_driver.py --help. Here it is:
Usage: doctest_driver.py [options] NAME ...
Options: --version show program's version number and exit -h, --help show this help message and exit
Actions (default=check): --check Verify the output of the doctest examples in the given files. -u, --update Update the expected output for new or out-of- date doctest examples in the given files. In particular, find every example whose actual output does not match its expected output; and replace its expected output with its actual output. You will be asked to verify the changes before they are written back to the file; be sure to check them over carefully, to ensure that you don't accidentally create broken test cases. --debug Verify the output of the doctest examples in the given files. If any example fails, then enter the python debugger.
Reporting: -v, --verbose Increase verbosity. -q, --quiet Decrease verbosity. -d, --udiff Display test failures using unified diffs. --cdiff Display test failures using context diffs. --ndiff Display test failures using ndiffs.
Output Comparison: --ellipsis Allow "..." to be used for ellipsis in the expected output. --normalize_whitespace Ignore whitespace differences between the expected output and the actual output.