Exception when running osi2read.py

[serge-m]

Describe the bug

Exception when running osi2read.py
Typo in the code

Describe how to reproduce the bug

Steps to reproduce the behavior:

1. Download compressed OSI file. https://github.com/OpenSimulationInterface/open-simulation-interface/blob/250137581977f962acef6c2003c3d61fb55fb964/tests/data/small_test.txt.lzma
2. Clone open-simulation-interface locally and install it as described in the official readme: https://github.com/OpenSimulationInterface/open-simulation-interface/tree/250137581977f962acef6c2003c3d61fb55fb964#install-for-python-usage
3. go to format directory, copy small_test.txt.lzma there.
4. python osi2read.py --data small_test.txt.lzma --output zaza.txt

Describe the expected behavior

Expected behavior: output text file is created.

Actual behavior: exception

/home/user/work/hackathon/open-simulation-interface/format/OSITrace.py:139: RuntimeWarning: Unexpected end-group tag: Not all data was converted
  message.ParseFromString(serialized_message[i+INT_LENGTH:i+INT_LENGTH+message_length])

Error
Traceback (most recent call last):
  File "/usr/lib/python3.6/unittest/case.py", line 59, in testPartExecutor
    yield
  File "/usr/lib/python3.6/unittest/case.py", line 605, in run
    testMethod()
  File "/home/user/work/hackathon/open-simulation-interface/tests/test_osi_trace.py", line 18, in test_osi_trace
    trace.make_readable(path_output, index=1)
  File "/home/user/work/hackathon/open-simulation-interface/format/OSITrace.py", line 239, in make_readable
    f.write(str(scenario.get_message_by_index(0)))
NameError: name 'scenario' is not defined

Show some screenshots

see stacktrace above

Describe the OS you are using

• OS: Ubuntu 18.04
• Language: Python
• Version 3.6.9

Additional context

none