Extra keys in `$ref` values within configuration should throw an error.

[pipermerriam]

• Populus Version: 1.6.x
• OS: all

What was wrong?

Any reference in a configuration file which has extra keys should throw an error at the time the configuration file is loaded and validated.

Example: https://gist.github.com/poiresel/0cf1aba442be17fead55c00fb2d3c546#file-populus-json-L110-L115

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[ice09]

Has this been fixed? I get now an error after setting the default account in any chain automatically. The eth.default_account is added exactly as described in this error, so to the reference, not the referred element. If added manually to the referred element, there is no error, but the default account is not set.

raise KeyError("Key '{0}' not found in {1}".format(key, self._wrapped))
KeyError: "Key 'provider.class' not found in {'provider': {'settings': {'port': 49187}}}"