EL8 build is failing because python3.6 isn't installed

The RPM builds on EL8 are failing because the relevant Python interpreter is not being installed:

+ /usr/bin/python3.6 setup.py build '--executable=/usr/bin/python3.6 -s'
/var/tmp/rpm-tmp.G5Ur0n: line 35: /usr/bin/python3.6: No such file or directory
error: Bad exit status from /var/tmp/rpm-tmp.G5Ur0n (%build)
    Bad exit status from /var/tmp/rpm-tmp.G5Ur0n (%build)
RPM build errors: