Removing pearson communication code

[annagav]

What are the relevant tickets?

Fix #4754

What's this PR do?

Remove legacy pearson code
Should also reomve the following config variables:

EXAMS_AUDIT_S3_BUCKET
EXAMS_AUDIT_AWS_ACCESS_KEY_ID
EXAMS_AUDIT_AWS_SECRET_ACCESS_KEY

How should this be manually tested?

nothing should break

[codecov-io]

Codecov Report

Merging #4765 (4f90ea7) into master (30afec9) will decrease coverage by 6.30%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master    #4765      +/-   ##
==========================================
- Coverage   94.39%   88.09%   -6.31%     
==========================================
  Files         512      193     -319     
  Lines       23349     8230   -15119     
  Branches      967      902      -65     
==========================================
- Hits        22040     7250   -14790     
+ Misses       1206      885     -321     
+ Partials      103       95       -8     

Impacted Files	Coverage Δ
exams/api.py	85.10% <ø> (+0.89%)	⬆️
...xams/management/commands/import_edx_exam_grades.py	0.00% <0.00%> (ø)
exams/signals.py	100.00% <ø> (ø)
exams/tasks.py	90.90% <ø> (-1.40%)	⬇️
exams/utils.py	100.00% <ø> (ø)
micromasters/settings.py	89.58% <ø> (-0.81%)	⬇️
micromasters/urls.py	80.00% <ø> (ø)
ui/views.py	93.54% <ø> (ø)
exams/constants.py	100.00% <100.00%> (ø)
grades/factories.py	100.00% <100.00%> (ø)
... and 297 more

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[pdpinch]

Can you change the typo in the PR title and your commits? It should be "pearson" with an "a". I'm just planning ahead for when we might have to search the repo for this change.

[rhysyngsun]

Functionally looking good but a few extra things we should get rid of:

• Move exams/pearson/constants.py to exams/constants.py
• In exams/tasks.py remove the PEARSON_* constants
• Remove unused pearson exam settings from settings.py
• Remove unused pearson exam env var definitions from app.json

[rhysyngsun]

@annagav looks like there's a test failure due to the removal of some settings.py stuff

[annagav]

@rhysyngsun I fixed the tests. Thank you!