Trap unicode decode errors when data is not valid utf-8

[lukebakken]

Fixes #769

[codecov]

Codecov Report

Merging #890 into master will decrease coverage by 0.06%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #890      +/-   ##
==========================================
- Coverage   81.94%   81.88%   -0.07%     
==========================================
  Files          21       21              
  Lines        3734     3743       +9     
  Branches      554      554              
==========================================
+ Hits         3060     3065       +5     
- Misses        523      527       +4     
  Partials      151      151

Impacted Files	Coverage Δ
pika/data.py	80.57% <66.66%> (-1.36%)	⬇️

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