registry: forbid direct access to Regexp.setValue.

This is not a regression; this was already forbidden before
23417b0675, and this commit was not
tagged/released yet at the moment I'm writing this one.

src/registry.py

@@ -785,6 +785,17 @@ class Regexp(Value):
         else:
             super().set(v)
 
+    def setValue(self, v):
+        """Don't call this function directly from plugins, it is subject
+        to change without notice."""
+        if v is not None and (not isinstance(v, tuple) or len(v) != 2):
+            raise InvalidRegistryValue(
+                'Can\'t setValue a regexp, there would be an inconsistency '
+                'between the regexp and the recorded string value. '
+                'Use .set() instead.')
+
+        super().setValue(v)
+
     def __call__(self):
         if self.value is None:
             return None

test/test_registry.py

@@ -183,6 +183,13 @@ class ValuesTestCase(SupyTestCase):
         v.set('')
         self.assertEqual(v(), None)
 
+    def testRegexpSetValue(self):
+        v = registry.Regexp(None, 'help')
+        self.assertRaises(registry.InvalidRegistryValue,
+                          v.setValue, r'foo')
+        self.assertRaises(registry.InvalidRegistryValue,
+                          v.setValue, re.compile(r'foo'))
+
     def testRegexpDefaultString(self):
         v = registry.Regexp('m/foo/', 'help')
         self.assertEqual(v(), re.compile('foo'))