Support Consul response code: 429

[kkzo]

Consul returns a 429 response code when: Some healthchecks are passing, at least one is warning (see https://www.consul.io/api-docs/agent/service).

This PR updates the callback handler to support response code 429.

[poppyred]

#22 will drop support v3.5,please fetch and merge new commit drop support v3.5

[codecov[bot]]

Codecov Report

Merging #24 (2b6fb25) into master (7aa1ff4) will decrease coverage by 0.09%. The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master      #24      +/-   ##
==========================================
- Coverage   94.45%   94.36%   -0.10%     
==========================================
  Files           6        6              
  Lines        1840     1845       +5     
==========================================
+ Hits         1738     1741       +3     
- Misses        102      104       +2     

Flag	Coverage Δ
unittests	94.36% <66.66%> (-0.10%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
consul/base.py	93.68% <66.66%> (-0.11%)	:arrow_down:

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[markblackman]

please merge as soon as convenient. If you do any kind of cluster monitoring with this package, the 429 response is a very common case.