convert: fix Python syntax in 'splice in' message
Instead of reporting
spliced in ['82544090e14fe18091e04f1fb0f0d7991cbe6e7e'] as parents of 369fd983d9e13330e9f12d9fce820deae84ea223
report
spliced in 82544090e14fe18091e04f1fb0f0d7991cbe6e7e as parents of 369fd983d9e13330e9f12d9fce820deae84ea223