Import All outputs warning instead of error if unrecognized files found

[isc-pbarton]

Fixes #291

Unit test does not really assert on error output, but still nice to have a little more coverage on Import All.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 42.67%. Comparing base (cbcdc5b) to head (7364173).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #826      +/-   ##
==========================================
+ Coverage   40.53%   42.67%   +2.14%     
==========================================
  Files          24       24              
  Lines        3264     3264              
==========================================
+ Hits         1323     1393      +70     
+ Misses       1941     1871      -70     

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