Fix sanitize function blowing on unicode characters

[tpazderka]

Close #421

• Any changes relevant to users are recorded in the CHANGELOG.md.
• The documentation has been updated, if necessary.

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[codecov-io]

Codecov Report

Merging #455 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #455      +/-   ##
==========================================
+ Coverage    58.2%   58.21%   +<.01%     
==========================================
  Files          61       61              
  Lines       11225    11227       +2     
  Branches     1907     1908       +1     
==========================================
+ Hits         6534     6536       +2     
  Misses       4147     4147              
  Partials      544      544

Impacted Files	Coverage Δ
src/oic/utils/sanitize.py	100% <100%> (ø)	⬆️

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