python: fix error handling while reading automata

* wrap/python/tests/run.in: Make it easier to run python with gdb.
* wrap/python/tests/automata-io.ipynb: Add test case.
* wrap/python/spot.py (spot.automata): Make sure p is defined in all
cases.
* src/hoaparse/hoascan.ll: Make sure we do not close a file that
hasn't been opened.

wrap/python/spot.py

@@ -137,6 +137,7 @@ def automata(*filenames):
 
     for filename in filenames:
         try:
+            p = None
             if filename[-1] != '|':
                 proc = None
                 p = hoa_stream_parser(filename, True)