Add support for specifying mutability when parsing a configuration

tests/ini/test_ini.py

@@ -94,4 +94,26 @@ def test_mutability():
         del config.key
         assert False, 'Expected TypeError'
     except TypeError:
-        pass
+        pass
+
+    configuration = '[section]\nkey=value'
+    config = INIConfiguration.from_string(configuration)
+    config.key1 = 'value1'
+
+    set_mutability(config, False)
+    try:
+        config.key2 = 'value2'
+        assert False, 'Expected TypeError'
+    except TypeError:
+        pass
+
+    config = INIConfiguration.from_string(configuration, mutable = False)
+
+    try:
+        config.key1 = 'value1'
+        assert False, 'Expected TypeError'
+    except TypeError:
+        pass
+
+    set_mutability(config, True)
+    config.key2 = 'value2'