Fix tornado master tests & instrument redis 4.3.5

[hmstepanek]

Overview

Fix tornado master tests & instrument redis 4.3.5

1. Drop 3.7 testing from tornado master.
   • Tornado master dropped support for 3.7
2. Instrument new redis 4.3.5 client methods.

[github-actions]

🦙 MegaLinter status: ❌ ERROR

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ PYTHON	bandit	1		0	2.72s
✅ PYTHON	black	1	0	0	0.47s
❌ PYTHON	flake8	1		18	0.29s
✅ PYTHON	isort	1	0	0	0.16s
✅ PYTHON	pylint	1		0	2.1s

See errors details in artifact MegaLinter reports on CI Job page
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff

MegaLinter is graciously provided by