fattureCCSR: added logging dialog to show action status

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>

utils.py

@@ -0,0 +1,16 @@
+"""Some useful utilities"""
+
+import os
+
+import exc
+
+def file_extension(file_path: str, allowed_ext: set = None) -> str:
+    """Return the file extension if that's in the allowed extension set"""
+    if file_path in (None, ""):
+        raise exc.NoFileError()
+    file_ext = os.path.splitext(file_path)[1]
+    if file_ext in (None, ""):
+        raise exc.NoFileExtensionError
+    if allowed_ext is not None and file_ext not in allowed_ext:
+        raise exc.WrongFileExtensionError
+    return file_ext