better error messages if option doesn't exists

tests/test_simple.py

@@ -0,0 +1,14 @@
+from json import loads
+from tiramisu_api import Config
+from pytest import raises
+
+
+def test_list_option():
+    filename = 'tests/data/boolean1.json'
+    with open(filename, 'r') as fh:
+        json = loads(fh.read())
+    #
+    config = Config(json)
+    opts = []
+    raises(AttributeError, "config.option('unknown').value.get()")
+    raises(AttributeError, "config.option('options.unknown').value.get()")

tiramisu_api/api.py

@@ -811,12 +811,16 @@ class Config:
             subpaths = path.split('.')[len(root):]
         else:
             subpaths = path.split('.')
+        current_subpath = 'root'
         for subpath in subpaths:
             if root_path:
                 root_path += '.' + subpath
             else:
                 root_path = subpath
-            schema = schema['properties'][root_path]
+            schema = schema['properties'].get(root_path)
+            if schema is None:
+                raise AttributeError(_(f'option "{subpath}" inconnue dans l\'optiondescription "{current_subpath}"'))
+            current_subpath = subpath
         return schema
 
     def isleader(self,