In Ruby, the Kernel class defined the `open` method, which is available
for (almost) every object. So creating a scope with the name `open`
generates a warning indicating we are overwriting the existing `open`
method.
While this warning is pretty much harmless and we could ignore it, it
generates a lot of noise in the logs. So I'm "undefining" the method
before generating the scope, so we don't get the warning all the time.
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