GZIP middleware consumes the HTTPResponse iterator, even if Content-Encoding is set to identity

[teh]

There's a check like

22 	        if response.has_header('Content-Encoding'):
23 	            return response

in the gzip middleware, but it gets executed _after_ the following check

        if response.status_code != 200 or len(response.content) < 200:
 	            return response

The "response.content" consumes an iterator passed to HttpResponse, which breaks e.g. in case of generators.

[Alex Gaynor]

Dupe of #6527, please search the archives before filing a new ticket.