[gi-docgen/wip/carlosg/multi-content-dir] utils: Raise exception for missing content files

[Emmanuele Bassi <ebassi src gnome org>]

commit e3a6d47ac0a32605dfd0d5c5eec98131404022d6
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Wed Jun 23 17:03:55 2021 +0100

    utils: Raise exception for missing content files
    
    If we can't find a content file specified in the project configuration,
    then we should bail out.

 gidocgen/utils.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gidocgen/utils.py b/gidocgen/utils.py
index ad538a5..c24a773 100644
--- a/gidocgen/utils.py
+++ b/gidocgen/utils.py
@@ -876,4 +876,4 @@ def find_extra_content_file(content_dirs, file):
         if os.path.isfile(full_path):
             return full_path
 
-    return None
+    raise FileNotFoundError(f"Content file {file} not found in any content directory")