[Python-ideas] Add dict.append and dict.extend

[Chris Angelico]

On Wed, Jun 6, 2018 at 4:18 PM, Chris Barker via Python-ideas
<python-ideas at python.org> wrote:
>
> Also -- seems kind of odd to raise a KeyError when the key IS there?!?

class DuplicateKeyError(LookupError): pass

Problem solved :)

ChrisA