Backed out changeset 1bc2220cd6ec The use of the error helpers creates an `<error/>` child element containing the error condition. This is however not allowed as per XEP-0198, which specifies that the error condition is to be a direct child of the `<failed/>` stream management element. This has triggered a fun reconnect loop in aioxmpp where it was reported by a user [1]. [1]: https://github.com/horazont/aioxmpp/issues/382

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