The package recaptcha-client doesn't install an __init__.py into the main module dir. This means other packages trying to use it will fail on the import. See also: https://warmcat.com/2017/08/12/mailman-captcha.html As far as I can see this can trivially be fixed by adding an empty __init__.py, e.g. by doing touch /usr/lib/python2.7/site-packages/recaptcha/__init__.py It would make sense if the ebuild would just do that.
See bug 611614
