Fix function serialization + deserialization where the function has values captured in its closure. (keras-team#8592)

* Fix function serialization + deserialization where the function
has values captured in its closure.
Also updated test.

* Fix PEP8 issue for Travis

* PEP8 linter fixes again...

* As per review request: https://github.com/fchollet/keras/pull/8592/files/c49ce42e5b5d9071df73854b95361b6915ce281f#r153083188
- Test now includes original function.
- Test is now modular with @pytest.mark.parametrize making it easy
  to add more tests in this category.

* Make ensure_value_to_cell function private (used inside func_load function)

Author: rh314

keras/utils/generic_utils.py

@@ -199,6 +199,27 @@ def func_load(code, defaults=None, closure=None, globs=None):
         code, defaults, closure = code
         if isinstance(defaults, list):
             defaults = tuple(defaults)
+
+    def ensure_value_to_cell(value):
+        """Ensures that a value is converted to a python cell object.
+
+        # Arguments
+            value: Any value that needs to be casted to the cell type
+
+        # Returns
+            A value wrapped as a cell object (see function "func_load")
+
+        """
+        def dummy_fn():
+            value  # just access it so it gets captured in .__closure__
+        cell_value = dummy_fn.__closure__[0]
+        if not isinstance(value, type(cell_value)):
+            return cell_value
+        else:
+            return value
+
+    if closure is not None:
+        closure = tuple(ensure_value_to_cell(_) for _ in closure)
     raw_code = codecs.decode(code.encode('ascii'), 'base64')
     code = marshal.loads(raw_code)
     if globs is None:

tests/keras/utils/generic_utils_test.py

@@ -78,9 +78,25 @@ def test_has_arg_positional_only():
     assert has_arg(pow, 'x') is False
 
 
-def test_func_dump_and_load():
-    def test_func():
-        return r'\u'
+@pytest.mark.parametrize(
+    'test_funcion_type',
+    ('simple function', 'closured function'))
+def test_func_dump_and_load(test_funcion_type):
+
+    if test_funcion_type == 'simple function':
+        def test_func():
+            return r'\u'
+    elif test_funcion_type == 'closured function':
+        def get_test_func():
+            x = r'\u'
+
+            def test_func():
+                return x
+            return test_func
+        test_func = get_test_func()
+    else:
+        raise Exception('Unknown test case for test_func_dump_and_load')
+
     serialized = func_dump(test_func)
     deserialized = func_load(serialized)
     assert deserialized.__code__ == test_func.__code__