Guys, I have some trouble finding the extensions directory in Plone5 to add my external method . I need to place a python script in that directory.
Add something like next line to your instance section in buildout.cfg
[instance]
zope-conf-additional = extensions ${buildout:directory}/Extensions
make a directory Extensions in your buildout directory and rerun buildout
Using External Methods is completely deprecated (although still working). Use brower views instead.
-aj