Build-require python3-devel for tests
    
    Make target for tests is created only if python is installed and that
    is controlled by %__python3 devel macro in spec file that exists only
    if python3-devel package is installed. Otherwise the test fails if
    generating documentation is disabled:
    
    Executing(%check): /bin/sh -e /var/tmp/rpm-tmp.O8YL29
    + umask 022
    + cd /builddir/build/BUILD
    + cd jsoncpp-1.8.3
    + /usr/bin/make -O -j6 -C x86_64-redhat-linux-gnu jsoncpp_check
    make: *** No rule to make target 'jsoncpp_check'.  Stop.