A little question about pycodestyle

I tried following the training Mastering Plone Theming - 5. Create a Plone Theme python package, but I got stalled when trying to run buildout for the tag bobtemplates.plone.git@1.0.5_boston. Here's the error message.

$ ./bin/buildout
Develop: '/Users/stevepiercy/projects/plone-theming-ibew/plonetheme.tango/.'
Version and requirements information containing pycodestyle:
Requirement of flake8-todo: pycodestyle<3.0.0,>=2.0.0
Requirement of flake8>=2.4.0: pycodestyle<2.1.0,>=2.0.0
Getting section code-analysis.
Initializing section code-analysis.
Installing recipe plone.recipe.codeanalysis[recommended].
Error: There is a version conflict.
We already have: pycodestyle 2.3.1
but flake8 3.0.4 requires 'pycodestyle<2.1.0,>=2.0.0'.
I looked through the issue tracker, and tried various version combinations in buildout.cfg, but to no avail.

These versions worked for me:

flake8 = 3.5.0
pycodestyle = 2.3.1

plone.recipe.zope2instance = 4.4.0