Make multimethods work with inheritance. (#3411)

Previously, this would fail with a NoSuchMethodError:

    class Package(object):
        # this is the default implementation
        def some_method(self):
            ...

    class Foo(Package):
        @when('platform=cray')
        def some_method(self):
            ...

        @when('platform=linux')
        def some_method(self):
            ...

This fixes the implementation of `@when` so that the superclass method
will be invoked when no subclass method matches.

Adds tests to ensure this works, as well.

0 files changed, 0 insertions, 0 deletions