Do not fail trying to decode list descriptions

There's all sorts of (undeclared) encodings in the list descriptions
we have in the databases, best if the API does not error out on them.

mailman_api/mailman.py

@@ -46,6 +46,19 @@ def _random_password():
     return os.urandom(12).encode('base64').rstrip('=\n')
 
 
+def _maybe_unicode(s):
+    # Try optimistically to guess the encoding of the list
+    # description (or just don't, nevermind).
+    try:
+        return unicode(s, 'utf-8')
+    except UnicodeEncodeError:
+        try:
+            return unicode(s, 'iso-8859-1')
+        except UnicodeEncodeError:
+            pass
+    return ''
+
+
 @app.route('/api/create_list', methods=('POST',))
 @tls_auth
 @to_json
@@ -89,7 +102,7 @@ def get_list_attrs():
         attrs = {
             'name': l,
             'public': 'no' if m.archive_private else 'yes',
-            'description': unicode(m.description, 'utf-8'),
+            'description': _maybe_unicode(m.description),
             'owners': list(set(m.owner[:])),
         }
         out.append(attrs)