Description of problem:
After https://github.com/rpm-software-management/rpm/commit/7ac3f07ac41a2760ed6dae65e63fe0b49aec6f6c#diff-8dfb47f00335d0da239fd9b61acaca5d %{python_sitelib}, %{python_sitearch}, %{python_version} macros stopped working.

Version-Release number of selected component (if applicable):
rpm-4.14.1-1.fc28

How reproducible: Easy


Steps to Reproduce:
1. mock -r fedora-rawhide-x86_64 --install python2-devel
2. mock -r fedora-rawhide-x86_64 --shell
3. rpm --eval '%{python_version}'
4. rpm --eval '%{python_sitelib}'
5. rpm --eval '%{python_sitearch}'

Actual results:
/usr/bin/python: can't open file '/usr/lib/rpm/python-macro-helper': [Errno 2] No such file or directory
/usr/bin/python: can't open file '/usr/lib/rpm/python-macro-helper': [Errno 2] No such file or directory
/usr/bin/python: can't open file '/usr/lib/rpm/python-macro-helper': [Errno 2] No such file or directory


Expected results:
2.7
/usr/lib/python2.7/site-packages
/usr/lib64/python2.7/site-packages

Additional info:
This breaks packages. See Bug 1536202.