Funny, I fixed what I thought were all the flake8 errors but after running code-analysis locally to see what Travis was complaining about it had this to say:
Flake8..........................[ FAILURE ] in 2.653s
/Users/kim/PloneBuilds/Plone-5.0.4-unified-clean/zinstance/src/collective.easyform/src/collective/easyform/actions.py:200:5: C901 'Mailer.get_addresses' is too complex (11)
It seems excessive (and dangerous) that I have to fix logic that isn't broken but is only stylistically objected to by this tool...