From Fedora Project Wiki
For convenience, the following macros are defined in EPEL and Fedora that you can use in conditionals. For each Python runtime, there are 2 versions of the macros: a must version (that says whether the packager must package for that runtime if possible) and a may version (that says that if the packager wants to, they may package for that runtime). Note that even if some macro currently expands to 1 an all Fedoras and EPELs, it maight change in the future.
%py3_must |
%py3_may |
%py2_must |
%py2_may
| |
|---|---|---|---|---|
| All Fedoras | 1 | 1 | 0 | 1 |
| EPEL 7 | 0 | 1 | 1 | 1 |
| EPEL 6 | 0 | 1 | 1 | 1 |
It's up to the packager whether they conditionalize on the must or may macros.