A large number of stylistic cleanups across django/db/
fixed a mis-importt in mysql/base.py
Use a more explicit check for whether these ids are None.
Tests passed when given patch was applied.
Fixed #18261 Clarified outer and inner directory in tutorial1.txt
Fixed #20346 cache middleware should vary on full URL
Revert "Tests passed when given patch was applied."

This reverts commit 9719798db4ddda76845bef69c136f46aeef5a9fa.
Revert "Fixed #18261 Clarified outer and inner directory in tutorial1.txt"

This reverts commit 8d82f128fc653925c54c410400b33a7353838a04.