Bump pyyaml from 5.3 to 5.4

[dependabot]

Bumps pyyaml from 5.3 to 5.4.

Changelog

Sourced from pyyaml's changelog.

5.4 (2021-01-19)

• yaml/pyyaml#407 -- Build modernization, remove distutils, fix metadata, build wheels, CI to GHA
• yaml/pyyaml#472 -- Fix for CVE-2020-14343, moves arbitrary python tags to UnsafeLoader
• yaml/pyyaml#441 -- Fix memory leak in implicit resolver setup
• yaml/pyyaml#392 -- Fix py2 copy support for timezone objects
• yaml/pyyaml#378 -- Fix compatibility with Jython

5.3.1 (2020-03-18)

• yaml/pyyaml#386 -- Prevents arbitrary code execution during python/object/new constructor

Commits

• 58d0cb7 5.4 release
• a60f7a1 Fix compatibility with Jython
• ee98abd Run CI on PR base branch changes
• ddf2033 constructor.timezone: _copy & deepcopy
• fc914d5 Avoid repeatedly appending to yaml_implicit_resolvers
• a001f27 Fix for CVE-2020-14343
• fe15062 Add 3.9 to appveyor file for completeness sake
• 1e1c7fb Add a newline character to end of pyproject.toml
• 0b6b7d6 Start sentences and phrases for capital letters
• c976915 Shell code improvements
• Additional commits viewable in compare view

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[codecov]

Codecov Report

Merging #3045 (3c8f1be) into hotfixes (28587f8) will increase coverage by 4.91%.
The diff coverage is 92.92%.

@@ Coverage Diff @@## hotfixes #3045 +/- ##
============================================
+ Coverage 80.80% 85.71% +4.91% 
============================================
Files 281 298 +17 Lines 12659 15879 +3220 ============================================
+ Hits 10229 13611 +3382 + Misses 2430 2268 -162 

Impacted Files	Coverage Δ
contentcuration/contentcuration/decorators.py	56.60% <50.00%> (-37.60%)	⬇️
...ntentcuration/contentcuration/db/models/manager.py	91.20% <90.98%> (-8.80%)	⬇️
contentcuration/contentcuration/forms.py	82.35% <94.04%> (+33.89%)	⬆️
contentcuration/contentcuration/api.py	92.06% <100.00%> (+1.43%)	⬆️
...tentcuration/contentcuration/context_processors.py	100.00% <100.00%> (ø)
...ontentcuration/contentcuration/db/advisory_lock.py	100.00% <100.00%> (ø)
...tcuration/contentcuration/db/models/expressions.py	93.33% <100.00%> (-6.67%)	⬇️
...entcuration/contentcuration/db/models/functions.py	100.00% <100.00%> (ø)
...ation/contentcuration/tests/test_rest_framework.py	36.93% <0.00%> (-63.07%)	⬇️
contentcuration/contentcuration/utils/format.py	21.05% <0.00%> (-49.54%)	⬇️
... and 181 more

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[rtibbles]

Seems like the specific vulnerability should not be something affecting us - so no need to expedite this.