All our Python specs have variations on:
# We want to byte-compile the .py files within the packages using the new
# python3 binary.
#
# Unfortunately, rpmbuild's infrastructure requires us to jump through some
# hoops to avoid byte-compiling with the system python 2 version:
# /usr/lib/rpm/redhat/macros sets up build policy that (amongst other things)
# defines __os_install_post. In particular, "brp-python-bytecompile" is
# invoked without an argument thus using the wrong version of python
# (/usr/bin/python, rather than the freshly built python), thus leading to
# numerous syntax errors, and incorrect magic numbers in the .pyc files. We
# thus override __os_install_post to avoid invoking this script:
%global __os_install_post /usr/lib/rpm/brp-compress \
%{!?__debug_package:/usr/lib/rpm/brp-strip %{__strip}} \
/usr/lib/rpm/brp-strip-static-archive %{__strip} \
/usr/lib/rpm/brp-strip-comment-note %{__strip} %{__objdump} \
/usr/lib/rpm/brp-python-hardlink
# to remove the invocation of brp-python-bytecompile, whilst keeping the
# invocation of brp-python-hardlink (since this should still work for python3
# pyc/pyo files)
This effectively freezes the brp policies to the given list and disables all of the rest.
Therefor i.e. the shebang mangling never took place for the pythons themselves.
The proper way of doing this is:
F28+:
%undefine __brp_python_bytecompile
F26, F27:
%global __os_install_post %(echo '%{__os_install_post}' | sed -e 's!/usr/lib[^[:space:]]*/brp-python-bytecompilespace:.*$!!g')
See https://fedoraproject.org/wiki/Packaging:Python_Appendix#Manual_byte_compilation