iotests/297: Add get_files() function

Split out file discovery into its own method to begin separating out
configuration/setup and test execution.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-id: 20211019144918.3159078-4-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

tests/qemu-iotests/297

@@ -21,6 +21,7 @@ import re
 import shutil
 import subprocess
 import sys
+from typing import List
 
 import iotests
 
@@ -54,10 +55,14 @@ def is_python_file(filename):
             return False
 
 
-def run_linters():
+def get_test_files() -> List[str]:
     named_tests = [f'tests/{entry}' for entry in os.listdir('tests')]
     check_tests = set(os.listdir('.') + named_tests) - set(SKIP_FILES)
-    files = [filename for filename in check_tests if is_python_file(filename)]
+    return list(filter(is_python_file, check_tests))
+
+
+def run_linters():
+    files = get_test_files()
 
     iotests.logger.debug('Files to be checked:')
     iotests.logger.debug(', '.join(sorted(files)))