Fixed #21304 -- Typo in docs/topics/testing/advanced.txt

Thanks joao at silvaneves.org for the report.
Added 1.5.5 and 1.4.9 release notes
Fixed #21307 -- Moved TransRealMixin to django.test.utils.
Fixed E225 pep8 warnings.
Workaround admin scripts test failures on Windows+Python 3.

Change strategy used to examine instrumented output to acommodate the
fact that on Windows, where the path separator is '\', repr() of Python
modules has changed in Python 3 to use escaped backslashes in the FS
path section (e.g.
'C:\\python3x\\Lib\\site-packages\\django\\contrib\\auth\\models.py')
without having to special-case based on platform.
Fixed #13245: Explained Oracle's behavior w.r.t db_table
and how to prevent table-name truncation

Thanks russellm & timo for discussion, and timo for review.
Fixed #21298 -- Fixed E301 pep8 warnings
Removed unused imports (or marked them flake8 ignore).