fix: Exclude external directory when generating python report

python/private/stage2_bootstrap_template.py

@@ -364,6 +364,7 @@ def _maybe_collect_coverage(enable):
                 # Pipes can't be read back later, which can cause coverage to
                 # throw an error when trying to get its source code.
                 "/dev/fd/*",
+                "*/external/*",
             ],
         )
         cov.start()