Could you please provide the results of?

python3 -c "import locale; print(locale.getlocale())"

('en_US', 'UTF-8')

Note that I believe the only place, where my native language can show up is the default / curent keyboard layout. But there possibly may be other ways I do not know about.

I have run into similar issue (date in Czech). I have managed to work around it by explicitly setting the LC_TIME variable: LC_TIME=en_US.utf-8 fedpkg module-build-local works as expected.

The locale function might be misleading, since without argument it queries only LC_CTYPE.

@mkoncek @jstanek Could you please add -d -v to fedpkg and run again?

@cqi $ fedpkg -d -v module-build-local -s platform:f30 in https://src.fedoraproject.org/modules/newsboat/tree/latest

Logs: https://paste.fedoraproject.org/paste/zVAYsOSDqT9fDVY7A8znrw

2019-07-23 10:52:02,530 - PoolThread-twisted.internet.reactor-0 - MBS.builder.utils - INFO - Executing command: ['rpmbuild', '-bs', 'module-build-macros.spec', '--define', '_topdir /tmp/module_build_service-build-macros5r9emf1x', '--define', '_sourcedir /tmp/module_build_service-build-macros5r9emf1x/SOURCES'], stdout log: /dev/null

MBS should not run rpmbuild on local system, it should be done in mock. End of the story.

Commit 4b4428a9 fixes this issue

This issue has been migrated to Fedora Forge:
https://forge.fedoraproject.org/koji/mbs/issues/1214

Please continue any further discussion there.