Synchronizing HttpRequest.headers on HttpRequest.META mutation

[Chris Wesseling]

I bumped into this old WONTFIX. And I agree with the decision not fix it in the way proposed by OP. But the current behaviour can be very confusing:

https://code.djangoproject.com/ticket/32023#comment:3

That  `del ` I propose would be free if nothing has accessed `headers` yet or nothing will be accessing `headers`. But would sync the contents, at the cost of an `if` in the `META` mutators.

Note even the quoted comment on the PR, suggest to mutate `META` directly.