cmd-buildprep: Add base unimplemented methods
This is a common pattern to signal that anything that subclasses us is
expected to implement these methods.
@@ -79,6 +79,12 @@ class Fetcher(object):
self.fetch_impl(url, dest)
return dest
+ def fetch_impl(self, url, dest):
+ raise NotImplementedError
+
+ def exists_impl(self, url):
+ raise NotImplementedError
+
def fetch_json(self, path):
return load_json(self.fetch(path))
