Refs #15667 -- Prevented newlines in attrs.html widget rendering.

Removed the trailing newline from widget attrs.html template.
The solution may be revisited by fixing refs #9198 but not
for Django 1.11.

Thanks Dmitry Ivanchenko for the report and Preston Timmons for advice.

django/forms/templates/django/forms/widgets/attrs.html

@@ -1 +1 @@
-{% for name, value in widget.attrs.items %} {{ name }}{% if not value is True %}="{{ value }}"{% endif %}{% endfor %}
+{% for name, value in widget.attrs.items %} {{ name }}{% if not value is True %}="{{ value }}"{% endif %}{% endfor %}

tests/forms_tests/widget_tests/base.py

@@ -17,11 +17,12 @@ class WidgetTest(SimpleTestCase):
         cls.renderers = [cls.django_renderer] + ([cls.jinja2_renderer] if cls.jinja2_renderer else [])
         super(WidgetTest, cls).setUpClass()
 
-    def check_html(self, widget, name, value, html='', attrs=None, **kwargs):
+    def check_html(self, widget, name, value, html='', attrs=None, strict=False, **kwargs):
+        assertEqual = self.assertEqual if strict else self.assertHTMLEqual
         if self.jinja2_renderer:
             output = widget.render(name, value, attrs=attrs, renderer=self.jinja2_renderer, **kwargs)
             # Django escapes quotes with '"' while Jinja2 uses '"'.
-            self.assertHTMLEqual(output.replace('"', '"'), html)
+            assertEqual(output.replace('"', '"'), html)
 
         output = widget.render(name, value, attrs=attrs, renderer=self.django_renderer, **kwargs)
-        self.assertHTMLEqual(output, html)
+        assertEqual(output, html)

tests/forms_tests/widget_tests/test_widget.py

@@ -1,12 +1,17 @@
 from __future__ import unicode_literals
 
 from django.forms import Widget
-from django.test import SimpleTestCase
+from django.forms.widgets import Input
+
+from .base import WidgetTest
 
 
-class WidgetTests(SimpleTestCase):
+class WidgetTests(WidgetTest):
 
     def test_value_omitted_from_data(self):
         widget = Widget()
         self.assertIs(widget.value_omitted_from_data({}, {}, 'field'), True)
         self.assertIs(widget.value_omitted_from_data({'field': 'value'}, {}, 'field'), False)
+
+    def test_no_trailing_newline_in_attrs(self):
+        self.check_html(Input(), 'name', 'value', strict=True, html='<input type="None" name="name" value="value" />')