Support bytes in assertXMLEqual()/assertXMLNotEqual().

[Joe Germuska]

In writing a test case, I found that passing the test client's response.content object into TestCase.assertXMLEqual() resulted in this error: a bytes-like object is required, not 'str'

In tracing the code, this originates from ​django.test.utils.compare_xml, where string literals \\n and \n are passed to replace() even though the types of want and got (particularly got) may be bytes and not str.

The workaround is to decode the response content before calling assertXMLEqual (response.content.decode('utf-8')) and to pass the assertion comparison ("want") also as a string, but if this method is going to be used in the testing framework, it seems that it should tolerate directly passing in response.content, even if that's a bytes.

[Mariusz Felisiak]

It's ​documented that assertXMLEqual() and assertXMLNotEqual() accept strings. I don't think we would like to complicate these methods, you can always use response.content.decode() (as you've already pointed out).