Fix: Do not bother asserting exception message content

[localheinz]

This PR

• stops asserting the exception message content

💁‍♂ Since we have dedicated exceptions now, we don't need to bother with it.

[codecov]

Codecov Report

Merging #138 into master will not change coverage by %.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #138   +/-   ##
=========================================
  Coverage     98.01%   98.01%           
  Complexity       72       72           
=========================================
  Files            12       12           
  Lines           202      202           
=========================================
  Hits            198      198           
  Misses            4        4           

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