AttributeError: 'PyOxidizerFinder' object has no attribute 'get_filename'

```py
ERROR: test_decorators (test.test_pyclbr.PyclbrTest)
----------------------------------------------------------------------
Traceback (most recent call last):
File "test.test_pyclbr", line 156, in test_decorators
self.checkModule('test.pyclbr_input', ignore=['om'])
File "test.test_pyclbr", line 67, in checkModule
dict = pyclbr.readmodule_ex(moduleName)
File "pyclbr", line 116, in readmodule_ex
File "pyclbr", line 154, in _readmodule
File "pyclbr", line 175, in _readmodule
AttributeError: 'PyOxidizerFinder' object has no attribute 'get_filename'
```
https://docs.python.org/3/library/importlib.html#importlib.abc.ExecutionLoader

Start with test.test_pyclbr.test_decorators and the pyclbr.readmodule_ex traceback, then compare PyOxidizerFinder with the importlib.abc.ExecutionLoader documentation linked in the issue. Done means the reported AttributeError is resolved and the test passes.

Written by the indexing model from the issue text.