analyzing Kaitai Structs fails on missing 'pkg_ressources' python module

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If your system python is not 3.9 you're pretty screwed on analizing Kaitai Structs:

```Analyzer Plugin Error: Plugin 'Kaitai Struct' reported an error with its processing: Failure Running parser in Python:
Python stderr:
Traceback (most recent call last):
File "/tmp/HobbitsPythonrBHuvX/thescript.py", line 162, in parse_data
struct_module = importlib.__import__(package_name, fromlist=[class_name])
File "", line 1109, in __import__
File "", line 1030, in _gcd_import
File "", line 1007, in _find_and_load
File "", line 986, in _find_and_load_unlocked
File "", line 680, in _load_unlocked
File "", line 850, in exec_module
File "", line 228, in _call_with_frames_removed
File "/tmp/hobbits-GGgAzl/png.py", line 3, in
from pkg_resources import parse_version
ModuleNotFoundError: No module named 'pkg_resources'
```

Start by reproducing Kaitai Struct analysis with a system Python version other than 3.9 and inspect the reported import failure for pkg_resources. Trace how the analyzer invokes the generated parser; done means the analysis completes without ModuleNotFoundError.

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