Added tests for conditional_content_removal.

Refs #7581. Thanks mrmachine.
Removed inaccurate statement from the StreamingHttpResponse docs.

Iterators will be closed for both regular and streaming responses;
this shouldn't be described as a difference.
Fixed #19157 -- Removed test-only string from translatable strings

Thanks Alexey Boriskin for the report. Refs #18240.
Cleaned up i18n regression tests
Fixed #19162 -- Wrong indentation.
Fixed #13222 -- Repeated iteration of HttpResponse

Thanks teepark for the report and grahamd for his insights.
Merge pull request #460 from JanBednarik/ticket_19162

Fixed #19162 -- Wrong indentation.
Reverted 6a64822bf4632707212314a25a843c862bdb3874.

This commit caused every test that does two or more assertContains to
fail, because of #6527. It also made HttpResponse non-pickleable.

Refs #13222.
Fixed #19164 -- Fixed diffsettings command broken in fix for #18545.

Thanks Mario César for the report and draft patch.
Fixed #19088 -- Always escape % inside blocktrans tag

Thanks vlinhart for the report and Łukasz Rekucki for the patch.
Fixed #19176 -- Typo in copy-pasted error message.

Thanks maxirobaina for the report.
Fixed a DeprecationWarning under Python 3.
Fixed #6527 -- Provided repeatable content access

in HttpResponses instantiated with iterators.
Fixed #13222 -- Made HttpResponse iterable once

response.content can be accessed many times as desired, and always
returns the same result.

iter(response) works only once and consumes the iterator.
Removed a function that is already fully implemented by a base class.
Fixed #9471 - Expanded ModelAdmin.raw_id_fields docs; thanks adroffne for the suggestion.
Remove a case that is no longer reachable in encodings.py.

This case was originally designed to handle Exception's which didn't gracefully support coercing themselves to unicode. However, because it lives in the `else` case of `if hasattr(s, '__unicode__'):` we can be sure it's no longer reachable in djanog anymore, because since Python 2.5 exception has subclassed object, which means Exception objects always have an __unicode__ method.
Fixed #18796 -- Refactored conversion to bytes in HttpResponse

Thanks mrmachine for the review.
Add 'page_kwarg' attribute to `MultipleObjectMixin`, removing hardcoded 'page'.
Test for `ListView.page_kwarg`