Replace assertIs assertion with assertEqual for string literals in tests

[aleksandr-shtaub]

Fixes wrong assertion method in "perfect numbers" tests.

Refs.:

• Emit a syntax warning for "is" with a literal python/cpython#79031
• https://flake8.pycqa.org/en/latest/user/error-codes.html (F632)

[BethanyG]

Hi @aleksandr-shtaub 👋🏽

Thanks for taking the time to submit a PR! Unfortunately, these changes have been made in the wrong place.

We use a test generator to automatically produce practice exercise test files. They're not intended to be edited directly.
To make the change, you will need to edit the jinja2 template for this exercise and then regenerate the test file by running the generator. You'll need to have both a clone of the Python repo and the problem-specifications repo. From python/ on your cloned Python repo:

./bin/generate_tests.py perfect-numbers

Both the jinja2 template and the re-generated file should then be checked in to the PR.

Let me know if you have any questions.

[aleksandr-shtaub]

Hi @BethanyG,

Interesting, thank you for the info!
I did a fixup commit.

[BethanyG]

Nice work. Many thanks! 🌟