Fix static test filler requiring a __init__.py without any python tests in the folder

[marioevz]

          One caveat I found when using the static state test loader is that this line fails if the yml or json file is found in a folder that does not have a `__init__.py` file with the following error:

Exception has occurred: AssertionError
Could not obtain a node for scope "Scope.Module" for function <FillerTestItem NoSrcAccount1559[fork_Prague-state_test-v=0-g=0-d=0]>
AssertionError: Could not obtain a node for scope "Scope.Module" for function <FillerTestItem NoSrcAccount1559[fork_Prague-state_test-v=0-g=0-d=0]>

During handling of the above exception, another exception occurred:

  File "/home/marioevz/Development/Eth/execution-spec-tests/src/pytest_plugins/refiller/refiller.py", line 287, in setup
    self.params[fixture_name] = request.getfixturevalue(fixture_name)
                                ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
AssertionError: Could not obtain a node for scope "Scope.Module" for function <FillerTestItem NoSrcAccount1559[fork_Prague-state_test-v=0-g=0-d=0]>

Note: NoSrcAccount1559 is the name of the test.

Originally posted by @marioevz in #1336 (comment)