use pyyaml beta with security fix

[fmigneault]

require beta version minimum of yaml until they fix and release 4.2/5.1 versions
yaml/pyyaml#243
yaml/pyyaml#193
yaml/pyyaml#74

[codecov-io]

Codecov Report

Merging #156 into master will decrease coverage by 0.18%.
The diff coverage is 64.47%.

@@            Coverage Diff             @@
##           master     #156      +/-   ##
==========================================
- Coverage    68.3%   68.12%   -0.19%     
==========================================
  Files          97       96       -1     
  Lines        6857     6889      +32     
==========================================
+ Hits         4684     4693       +9     
- Misses       2173     2196      +23

Impacted Files	Coverage Δ
magpie/register.py	40.24% <0%> (-0.12%)	⬇️
magpie/adapter/magpieprocess.py	0% <0%> (ø)	⬆️
magpie/definitions/typedefs.py	0% <0%> (-10%)	⬇️
magpie/api/management/resource/resource_views.py	71.15% <0%> (-0.55%)	⬇️
.../438c27ec1c9_normalize_constraint_and_key_names.py	62.5% <100%> (ø)	⬆️
magpie/api/login/esgfopenid.py	63.15% <100%> (ø)	⬆️
magpie/api/home/home.py	100% <100%> (ø)	⬆️
magpie/definitions/pyramid_definitions.py	100% <100%> (ø)	⬆️
magpie/api/management/service/service_views.py	97.56% <100%> (ø)	⬆️
magpie/app.py	92.15% <100%> (ø)
... and 27 more

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