Clarify yaml read warnings

[iguinn]

Clarify yaml read warnings by using str (!s) instead of repr (!r) in formatting string.

With repr:

With str:

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 92.44%. Comparing base (5b17622) to head (7f43c51).
⚠️ Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
src/dbetto/textdb.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #60      +/-   ##
==========================================
+ Coverage   91.72%   92.44%   +0.72%     
==========================================
  Files           6        6              
  Lines         568      596      +28     
==========================================
+ Hits          521      551      +30     
+ Misses         47       45       -2     

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