Display emojis with test results

[joelostblom]

• This PR adds emojis for individual test that pass or fail, as well as if all tests pass. I think the emojis for individual tests makes it easier to quickly spot what is right and what is wrong, and it gives a certain satisfaction to see many green checkmarks (personal opinion of course).
• Although the emojis are green and red, I try to choose sufficiently different shapes to not be an issue for people with color vision deficiencies.
• The addition of the failure message will also facilitate implementing Hide traceback and verbose otter output to only show assertion message instead #419 where the traceback is optionally removed.
• The random positive emoji when all tests passes is similar to what test_that in R does and is more of a fun touch.

Individual tests:

All tests:

[chrispyles]

Can you also look at adding the emojis to the new exception-based test files? I think editing message in the run() method should be sufficient: https://github.com/ucbds-infra/otter-grader/blob/master/otter/test_files/exception_test.py#L156

[chrispyles]

@joelostblom can you also add an entry to the changelog?

[joelostblom]

Can you also look at adding the emojis to the new exception-based test files?

@chrispyles I had a go at doing this the same way as for the regular ok-tests, but there seem to be not test files in otter CI to check exception based tests so not sure I have gotten it right. I am not familiar with this new format of tests and I am not clear on the differences versus the old format after reading the docs, so I might need some help if there are significant other changes needed.

[codecov]

Codecov Report

Base: 72.53% // Head: 72.17% // Decreases project coverage by -0.36% ⚠️

Coverage data is based on head (cc66129) compared to base (7c00b46).
Patch coverage: 37.50% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #533      +/-   ##
==========================================
- Coverage   72.53%   72.17%   -0.37%     
==========================================
  Files          64       62       -2     
  Lines        3921     3748     -173     
==========================================
- Hits         2844     2705     -139     
+ Misses       1077     1043      -34     

Impacted Files	Coverage Δ
otter/test_files/exception_test.py	33.75% <0.00%> (ø)
otter/test_files/abstract_test.py	75.36% <25.00%> (-0.38%)	⬇️
otter/test_files/ok_test.py	100.00% <100.00%> (ø)
otter/utils.py
otter/__init__.py

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[chrispyles]

but there seem to be not test files in otter CI to check exception based tests so not sure I have gotten it right

+1. I need to add tests for this behavior.