As far as I know, you can’t.
You can disable errors or warnings user wide, or per project. See the documentation.
Instead, you can use the # noqa comment at the end of a line, to skip that particular line (see patch 136). Of course, that would skip all PEP8 errors.
The main author argues against source file noise, so they suggested # pep8 comments don’t get included.
Note that there is also nopep8, which is the equivalent. noqa (which stands for No Quality Assurance was added in version 1.4.1 to support people running pyflakes next to pep8.