Update v1.2.1 release notes and CHANGELOG with CI test fix

Author: mmcky

CHANGELOG.md

@@ -8,6 +8,8 @@
   - Added defensive check before removing 'std-ref' class in `UpdateReferencesToEnumerated` transform
   - The 'std-ref' class may not be present in all build scenarios (particularly LaTeX/PDF builds)
   - Fix ensures compatibility across different Sphinx builders and versions
+- Fixed flaky CI tests caused by matplotlib font cache warning appearing in test output
+  - Added regex patterns to strip matplotlib font cache stderr messages from test regression fixtures
 
 ## [v1.2.0](https://github.com/executablebooks/sphinx-exercise/tree/v1.2.0) (2025-11-05)
 

docs/source/releases/v1.2.1.md

@@ -8,7 +8,11 @@ This is a patch release that fixes a bug causing build failures in LaTeX/PDF out
 
 ### LaTeX/PDF Build Failure
 
-Fixed a `ValueError: list.remove(x): x not in list` error that occurred when building LaTeX/PDF documentation with sphinx-exercise v1.2.0.
+Fixed a `ValueError: list.remove(x): x not in list` error that occurred when building LaTeX/PDF documentation with sphinx-exercise v1.2.0 (#82).
+
+### CI Test Reliability
+
+Fixed flaky test failures in GitHub Actions CI caused by matplotlib font cache initialization warnings appearing in test output.
 
 **Issue:**
 - The `UpdateReferencesToEnumerated` transform attempted to remove the `'std-ref'` CSS class from inline reference nodes