This is a tracking bug for Change: Python 3 C.UTF-8 locale
For more details, see: https://fedoraproject.org//wiki/Changes/python3_c.utf-8_locale
The standalone Python 3.6 binary will automatically attempt to coerce the C locale to C.UTF-8, unless the new PYTHONCOERCECLOCALE environment variable is set to 0.
Switching to MODIFIED as this Change is already in the Fedora 26 Alpha 1.1 compose.
On 2017-May-16 we reached the "Change Checkpoint: 100% Code Complete Deadline" milestone for Fedora 26 release. At this point all the Changes not at least in "ON_QA" state should be brought to FESCo for review. Please update the state of this bug to "ON_QA" if it is already 100% completed. Please let me know in case you have any trouble with the implementation and the Change needs any help or review.
This Change is going to be reviewed on a FESCo meeting: https://pagure.io/fesco/issue/1710
Actually this modification breaks many packages that uses "testsuite" (autoconf stuff) and/or "autoconf" since "autoconf" / "testsuite" enforce LC_ALL=C and testsuite check stderr (by default) and so tests will fail since stderr is not empty.
An example of packages that was broken with this modification is "openvswitch"
A workaround in a spec file could be to set PYTHONCOERCECLOCALE=0 in %check and/or %build
The implementation has been changed. While python3 will actually change the locale, it will not print a warning to stderr.
Just adding a link to https://bugzilla.redhat.com/show_bug.cgi?id=1404918 for traceability to the actual implementation BZ, since the F26 change proposal page links here, and PEP 528 and Victor Stinner's recent article at https://vstinner.github.io/posix-locale.html both link to the change proposal page.