skip divine tests when divine does not understand compile --help

Fixes #235, reported by Henrich Lauko.

* python/spot/ltsmin.i: Catch CalledProcessError.
* NEWS: Mention the bug.
* THANKS: Add Henrich.

NEWS

@@ -6,6 +6,11 @@ New in spot 2.3.1.dev (not yet released)
     can be output using --stats=%x (output automaton) or --stats=%X
     (input automaton).
 
+  Bugs fixed:
+
+  - The tests using LTSmin's patched version of divine would fail
+    if the current (non-patched) version of divine was installed.
+
 New in spot 2.3.1 (2017-02-20)
 
   Tools:

THANKS

@@ -14,6 +14,7 @@ Felix Klaedtke
 František Blahoudek
 Gerard J. Holzmann
 Heikki Tauriainen
+Henrich Lauko
 Jan Strejček
 Jean-Michel Couvreur
 Jean-Michel Ilié

python/spot/ltsmin.i

 // -*- coding: utf-8 -*-
-// Copyright (C) 2016 Laboratoire de Recherche et Développement de
+// Copyright (C) 2016, 2017 Laboratoire de Recherche et Développement de
 // l'Epita (LRDE).
 //
 // This file is part of Spot, a model checking library.
@@ -120,8 +120,13 @@ def require(*tools):
             if shutil.which("divine") == None:
                 print("divine not available", file=sys.stderr)
                 sys.exit(77)
-            out = subprocess.check_output(['divine', 'compile', '--help'],
-                                          stderr=subprocess.STDOUT)
+            try:
+                out = subprocess.check_output(['divine', 'compile', '--help'],
+                                              stderr=subprocess.STDOUT)
+            except (subprocess.CalledProcessError):
+                print("divine does not understand 'compile --help'",
+                       file=sys.stderr)
+                sys.exit(77)
             if b'LTSmin' not in out:
                 print("divine available but no support for LTSmin",
                        file=sys.stderr)