This adds the Python files in the tests/ directory to be formatted with
./tools/codeformat.py. The basics/ subdirectory is excluded for now so we
aren't changing too much at once.
In a few places `# fmt: off`/`# fmt: on` was used where the code had
special formatting for readability or where the test was actually testing
the specific formatting.
Don't store final, failing value to the loop variable. This fix also
makes for .. range a bit more efficient, as it uses less store/load
pairs for the loop variable.
David Lechner