SyntaxError: 'return' outside function
In the particular context of running Buildout, this error is annoying, but harmless.
The reason it happens is that while running buildout, it compiles the Python files — which includes the "Python Script" type from Zope, which isn't a fully-formed Python file. Thus, the compiler thinks there is something wrong.
This error can safely be ignored if it's showing up when running Buildout.