Make Python operations stricter about types

[Fidget-Spinner]

Description

Fixes https://github.com/source-academy/py-slang/issues/39

Type of change

• [X] Breaking change (fix or feature that would cause existing functionality to not work as expected)

How to test

The example given in the issue should throw error now.

Checklist

• [ ] I have tested this code

[RichDom2185]

The tests seem to be failing?

[Fidget-Spinner]

I think the tests should pass now

[coveralls]

Pull Request Test Coverage Report for Build 9338381529

Details

• 14 of 96 (14.58%) changed or added relevant lines in 1 file are covered.
• 35 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.6%) to 81.532%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/stdlib/pylib.ts	14	96	14.58%
<!--	Total:	14	96	14.58%	-->

Files with Coverage Reduction	New Missed Lines	%
src/stdlib/pylib.ts	35	44.2%
<!--	Total:	35		-->

Totals
Change from base Build 8967380994:	-0.6%
Covered Lines:	10933
Relevant Lines:	13042

---

💛 - Coveralls

[Fidget-Spinner]

I need an approving review to merge it seems.

[RichDom2185]

I need an approving review to merge it seems.

The CI turned out to fall, that's why I dismissed my approval

[Fidget-Spinner]

@RichDom2185 CI passes now.