set_config now returns None instead of an empty string and have a test case.

tests.py

@@ -1000,6 +1000,16 @@ class TestYara(unittest.TestCase):
         r = next(it)
         self.assertTrue(r.identifier == 'test3')
 
+    def testSetConfig(self):
+
+        yara.set_config(max_strings_per_rule=1)
+
+        self.assertSyntaxError(['''
+            rule test { strings: $a = "1" $b = "2" condition: all of them }
+            '''])
+
+        yara.set_config(max_strings_per_rule=10000)
+
 
 if __name__ == "__main__":
     unittest.main()

yara-python.c

@@ -1836,21 +1836,28 @@ static PyObject* yara_set_config(
         &stack_size,
         &max_strings_per_rule))
   {
-    if(stack_size != 0) {
-      if((error = yr_set_configuration(YR_CONFIG_STACK_SIZE,
-				       &stack_size)) != ERROR_SUCCESS) {
+    if (stack_size != 0)
+    {
+      error = yr_set_configuration(
+          YR_CONFIG_STACK_SIZE,
+          &stack_size);
+
+      if ( error != ERROR_SUCCESS)
         return handle_error(error, NULL);
     }
-    }
-    if(max_strings_per_rule != 0) {
-      if((error = yr_set_configuration(YR_CONFIG_MAX_STRINGS_PER_RULE,
-				       &max_strings_per_rule)) != ERROR_SUCCESS) {
+
+    if (max_strings_per_rule != 0)
+    {
+      error = yr_set_configuration(
+          YR_CONFIG_MAX_STRINGS_PER_RULE,
+				  &max_strings_per_rule);
+
+      if (error != ERROR_SUCCESS)
         return handle_error(error, NULL);
     }
   }
-  }
 
-  return Py_BuildValue("");
+  Py_RETURN_NONE;
 }
 
 static PyObject* yara_compile(