Allow Python files not to be executable

.py files may be modules which are not standalone program, so allow
them not to be executable.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/scripts/check_files.py b/tests/scripts/check_files.py
index 13fee9d..c498117 100755
--- a/tests/scripts/check_files.py
+++ b/tests/scripts/check_files.py
@@ -161,9 +161,13 @@
 
     heading = "Incorrect permissions:"
 
+    # .py files can be either full scripts or modules, so they may or may
+    # not be executable.
+    suffix_exemptions = frozenset({".py"})
+
     def check_file_for_issue(self, filepath):
         is_executable = os.access(filepath, os.X_OK)
-        should_be_executable = filepath.endswith((".sh", ".pl", ".py"))
+        should_be_executable = filepath.endswith((".sh", ".pl"))
         if is_executable != should_be_executable:
             self.files_with_issues[filepath] = None