Fix error type

Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
diff --git a/scripts/config.py b/scripts/config.py
index 3ee21d1..839e26a 100755
--- a/scripts/config.py
+++ b/scripts/config.py
@@ -413,8 +413,8 @@
                     filename = candidate
                     break
             else:
-                raise ValueError(f'{name} configuration file not found: '
-                                 f'{filename if filename else default_path}')
+                raise FileNotFoundError(f'{name} configuration file not found: '
+                                        f'{filename if filename else default_path}')
 
         self.filename = filename
         self.templates = []