Description of problem: When PYTHON_DISALLOW_AMBIGUOUS_VERSION is set to warn the exit status of python changes to 1 which can sometimes cause builds to fail. The spec at https://fedoraproject.org/wiki/Changes/Avoid_usr_bin_python_in_RPM_Build#Specification suggests than warn will only print a warning and only 1 change the exit status. Version-Release number of selected component (if applicable): python2-2.7.14-11.fc28.x86_64
This is nonsense. The actual problem I think is that gyp inspects stderr and aborts if it sees output there.