Remove miscellaneous Python 2 anachronisms

[cclauss]

% ruff check --select=UP009,UP018,UP021,UP039 --output-format=concise

mavftp.py:1241:21: UP018 [*] Unnecessary `bytes` call (rewrite as a literal)
mavutil.py:940:17: UP039 [*] Unnecessary parentheses after class definition
tests/snapshottests/test_wlua.py:91:9: UP021 [*] `universal_newlines` is deprecated, use `text`
tools/mavfft_isb.py:75:18: UP039 [*] Unnecessary parentheses after class definition
tools/mavftpdecode.py:33:16: UP018 [*] Unnecessary `bytes` call (rewrite as a literal)
tools/mavftpdecode.py:64:17: UP018 [*] Unnecessary `bytes` call (rewrite as a literal)
tools/python_array_test_recv.py:2:1: UP009 [*] UTF-8 encoding declaration is unnecessary
tools/python_array_test_send.py:2:1: UP009 [*] UTF-8 encoding declaration is unnecessary
Found 8 errors.
[*] 8 fixable with the `--fix` option.`

How was this tested?

localhost:

source .venv/bin/activate
python -m pytest  # 1 failed, 50 passed, 8 skipped, 1 warning in 16.02s -- tests/test_mavftp.py OSError: Address already in use

What other testing approaches should be considered?
What is our minimal supported Python? Python 3.7?

---

% ruff rule UP021

replace-universal-newlines (UP021)

Derived from the pyupgrade linter.

Fix is always available.

What it does

Checks for uses of subprocess.run that set the universal_newlines
keyword argument.

Why is this bad?

As of Python 3.7, the universal_newlines keyword argument has been
renamed to text, and now exists for backwards compatibility. The
universal_newlines keyword argument may be removed in a future version of
Python. Prefer text, which is more explicit and readable.

Example

import subprocess

subprocess.run(["foo"], universal_newlines=True)

Use instead:

import subprocess

subprocess.run(["foo"], text=True)

References

• Python 3.7 release notes
• Python documentation: subprocess.run