Fixed #25410 -- Fixed empty ClearableFileInput crash on Python 2.

Reverted "Fixes #24727 -- Prevented ClearableFileInput from masking
exceptions on Python 2" and added a regression test.

This reverts commit 5c412dd8a7.

tests/forms_tests/widget_tests/test_clearablefileinput.py

@@ -57,25 +57,6 @@ class ClearableFileInputTest(WidgetTest):
         self.assertIn('my<div>file', output)
         self.assertNotIn('my<div>file', output)
 
-    def test_html_does_not_mask_exceptions(self):
-        """
-        A ClearableFileInput should not mask exceptions produced while
-        checking that it has a value.
-        """
-        @python_2_unicode_compatible
-        class FailingURLFieldFile(object):
-            @property
-            def url(self):
-                raise RuntimeError('Canary')
-
-            def __str__(self):
-                return 'value'
-
-        widget = ClearableFileInput()
-        field = FailingURLFieldFile()
-        with self.assertRaisesMessage(RuntimeError, 'Canary'):
-            widget.render('myfile', field)
-
     def test_clear_input_renders_only_if_not_required(self):
         """
         A ClearableFileInput with is_required=False does not render a clear