_postproc_translate_options: fix syntax error

* python/spot/__init__.py: Here.
* tests/python/except.py: Add test.
* NEWS: Mention the issue.

NEWS

@@ -92,6 +92,10 @@ New in spot 2.8.5.dev (not yet released)
     consequence, some correct output could be larger than necessary
     (but still correct).
 
+  - calling spot.translate() with two conflicting preferences like
+    spot.translate(..., 'det', 'any') triggered a syntax error in the
+    Python code to handle this error.
+
 New in spot 2.8.5 (2020-01-04)
 
   Bugs fixed:

python/spot/__init__.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-# Copyright (C) 2014-2019  Laboratoire de
+# Copyright (C) 2014-2020  Laboratoire de
 # Recherche et Développement de l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
@@ -622,7 +622,7 @@ def _postproc_translate_options(obj, default_type, *args):
         nonlocal pref_, pref_name_
         if pref_ is not None and pref_name_ != val:
             raise ValueError("preference cannot be both {} and {}"
-                             .format(pref_name, val))
+                             .format(pref_name_, val))
         elif val == 'small':
             pref_ = postprocessor.Small
         elif val == 'deterministic':

tests/python/except.py

@@ -1,5 +1,5 @@
 # -*- mode: python; coding: utf-8 -*-
-# Copyright (C) 2018, 2019 Laboratoire de Recherche et Développement de
+# Copyright (C) 2018-2020 Laboratoire de Recherche et Développement de
 # l'Epita (LRDE).
 #
 # This file is part of Spot, a model checking library.
@@ -179,3 +179,12 @@ except RuntimeError as e:
     assert "requires a semi-deterministic input" in str(e)
 else:
     report_missing_exception()
+
+try:
+    spot.translate('F(G(a | !a) & ((b <-> c) W d))', 'det', 'any')
+except ValueError as e:
+    s = str(e)
+    assert 'det' in s
+    assert 'any' in s
+else:
+    report_missing_exception()