python.cc: isl_class::print: avoid different signs comparison warning
python.cc: isl_class::print: avoid different signs comparison warning

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

tobig/isl,nicolasvasilache/isl,inducer/isl-mirror,Meinersbur/isl,UBERTC/isl,UBERTC/isl,inducer/isl-mirror,PollyLabs/isl,nicolasvasilache/isl,BenzoSM/isl,Meinersbur/isl,UBERTC/isl,nicolasvasilache/isl,nicolasvasilache/isl,PollyLabs/isl,BenzoSM/isl,inducer/isl-mirror,nicolasvasilache/isl,inducer/isl-mirror,BenzoSM/isl,PollyLabs/isl,PollyLabs/isl,tobig/isl,PollyLabs/isl,UBERTC/isl,BenzoSM/isl,Meinersbur/isl,Meinersbur/isl,tobig/isl,tobig/isl,BenzoSM/isl,inducer/isl-mirror