Fix our new failure with Open FST
Traceback (most recent call last):
File "/home/forge/teamcity-agent/work/a0185dad9234e013/tests/python/efsm.py", line 59, in <module>
check(a, f + '.efsm')
File "/home/forge/teamcity-agent/work/a0185dad9234e013/tests/python/efsm.py", line 46, in check
CHECK_EQUIV(aut, normalize(aut.fstcat()))
RuntimeError: efstcompile failed: FATAL: FstCompiler: Bad state ID integer = "4294967294", source = /tmp/sh.uuXtRB/transitions.fsm, line = 1
We are clearly doing something that OpenFST does not like. Make a precise diagnostic about it, and fix our I/O routines to be compatible with it.