fix: read config data with bytes (python3)

[tomplus]

Ref: kubernetes-client/python-base#86

[codecov-io]

Codecov Report

Merging #41 into master will increase coverage by 0.05%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #41      +/-   ##
==========================================
+ Coverage   94.07%   94.13%   +0.05%     
==========================================
  Files          18       18              
  Lines        1182     1193      +11     
==========================================
+ Hits         1112     1123      +11     
  Misses         70       70

Impacted Files	Coverage Δ
kubernetes_asyncio/config/kube_config.py	93.23% <100%> (+0.07%)	⬆️
kubernetes_asyncio/config/kube_config_test.py	93.64% <100%> (+0.14%)	⬆️

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