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[westonruter]

Summary

Fixes #6076

Checklist

• My code is tested and passes existing tests.
• My code follows the Engineering Guidelines (updates are often made to the guidelines, check it out periodically).

[github-actions]

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[codecov]

Codecov Report

Merging #6082 (4e91000) into develop (8db37c3) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             develop    #6082   +/-   ##
==========================================
  Coverage      74.92%   74.92%           
  Complexity      5775     5775           
==========================================
  Files            231      231           
  Lines          17483    17484    +1     
==========================================
+ Hits           13099    13100    +1     
  Misses          4384     4384           

Flag	Coverage Δ	Complexity Δ
javascript	79.84% <ø> (ø)	0.00 <ø> (ø)
php	74.70% <100.00%> (+<0.01%)	5775.00 <0.00> (ø)

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Impacted Files	Coverage Δ	Complexity Δ
includes/sanitizers/class-amp-form-sanitizer.php	98.21% <100.00%> (+0.01%)	43.00 <0.00> (ø)

[pierlon]

Should this close #6076? This PR will only partly fix the issue (that is, adapting the shown error message).

[westonruter]

Yes, as #4191 will address the non-SEO aspect.