[Checkins] [zopefoundation/Products.SiteErrorLog] f4d129: Fix linting issue

[Jürgen Gmach]

  Branch: refs/heads/fix-lint
  Home:   https://github.com/zopefoundation/Products.SiteErrorLog
  Commit: f4d1294b69fdaec21f04fbf0ac1e0f91dd847f61
      https://github.com/zopefoundation/Products.SiteErrorLog/commit/f4d1294b69fdaec21f04fbf0ac1e0f91dd847f61
  Author: Jürgen Gmach <juergen.gmach at googlemail.com>
  Date:   2020-05-15 (Fri, 15 May 2020)

  Changed paths:
    M tox.ini

  Log Message:
  -----------
  Fix linting issue

... which arise with the new flake8 version.

`tests` is no longer a valid flake8 param, as it is no top level
directory.

As it is a subfolder of the `src` folder, it gets linted anyway.

modified:   tox.ini