.rpm build errors with Python3: unresolvable

[az0]

revision ab76ebd

CentOS 6: unresolvable
CentOS 7: succeeded
CentOS 8: unresolvable, nothing provides python3-devel
Fedora 30, 31: succeeded
RHEL 6: unresolvable
RHEL 7: unresolvable
openSUSE_Leap_42.3: failed Unknown tag: %py3_requires

[az0]

I set up a vanilla CentOS 8 system, and /usr/lib/rpm/macros defines %__python but not %__python2 or %__python3

On CentOS 7, %__python is /usr/bin/python, and there are no 2/3 versioned macros for Python

Fedora 31 defines no python macros

[az0]

On OBS, by default CentOS 7 and 8 do not install Python 3. On my CentOS 8 system, there is a package called python36, but when I put python36 in BuildRequires, OBS claims it is unresolvable.

SLE 11 does not have python3-setuptools

[az0]

On my local CentOS 8, I installed python-rpm-macros which adds more macros, but they don't look useful. For example, it defines %py_build() which uses python2.

After some tweaks, CentOS 8 is failing like this

[  112s] cd /home/abuild/rpmbuild/BUILDROOT/bleachbit-3.1.0-35.1.x86_64/usr/share/bleachbit && \
[  112s] python3 -O -c "import compileall; compileall.compile_dir('.')" && \
[  112s] python3 -c "import compileall; compileall.compile_dir('.')"
[  112s] /bin/bash: line 1: python3: command not found

On my CentOS 8 local machine, I have /usr/bin/python3 but not /usr/bin/python (unversioned).

Maybe the Makefile needs the full path?

[az0]

#769