Comment 3 for bug 1937173

Finally I found a command that fails in bad and works in good env

$ BRZ_CONCURRENCY=3 BRZ_HOME=debian/brzhome BRZ_PLUGIN_PATH=-site:-user LC_ALL=C.UTF-8 PYTHONPATH=/build/breezy-xbGxjH/breezy-3.2.1/.pybuild/cpython3_3.9_breezy/build python3.9 ./brz -Derror selftest -v breezy.tests.test_plugins.TestLoadingPlugins
=> BAD

Reducing concurrency makes no difference:
$ BRZ_PLUGIN_PATH=-site:-user LC_ALL=C.UTF-8 PYTHONPATH=/build/breezy-xbGxjH/breezy-3.2.1/.pybuild/cpython3_3.9_breezy/build python3.9 ./brz -Derror selftest -v breezy.tests.test_plugins.TestLoadingPlugins
=> Still bad

But one has to remember that running a single subtest of it works.
like:
$ BRZ_PLUGIN_PATH=-site:-user LC_ALL=C.UTF-8 PYTHONPATH=/build/breezy-xbGxjH/breezy-3.2.1/.pybuild/cpython3_3.9_breezy/build python3.9 ./brz -Derror selftest -v breezy.tests.test_plugins.TestLoadingPlugins.test_plugins_can_load_from_directory_with_trailing_slash
=> GOOD

Even running all of them one after the other works:
$ for t in test_plugins.TestLoadingPlugins.test_plugin_with_bad_api_version_reports test_plugins.TestLoadingPlugins.test_plugin_with_bad_name_does_not_load test_plugins.TestLoadingPlugins.test_plugin_with_error test_plugins.TestLoadingPlugins.test_plugin_with_error_suppress test_plugins.TestLoadingPlugins.test_plugins_can_load_from_directory_with_trailing_slash test_plugins.TestLoadingPlugins.test_plugins_from_different_dirs_can_demand_load test_plugins.TestLoadingPlugins.test_plugins_with_the_same_name_are_not_loaded; do BRZ_PLUGIN_PATH=-site:-user LC_ALL=C.UTF-8 PYTHONPATH=/build/breezy-xbGxjH/breezy-3.2.1/.pybuild/cpython3_3.9_breezy/build python3.9 ./brz -Derror selftest -v $t; printf "\n\n\n\n\n\n\n\n\n"; done

=> All of them are good now, but while running them at once as shown above they fail.