update future import test

Fixed test suite to not rely upon ancient "future division" statement to
test the :paramref:`.Template.future_imports` feature.   The test is
replaced with one that tests only the rendering, not the ultimate effect.

Also updates ancient documentation that also refers to this now defunct
future statement

Fixes: #408
Change-Id: I3e7d5bceb31fb141e2ea513d099be267dda1abe2

doc/build/unreleased/408.rst

@@ -0,0 +1,7 @@
+.. change::
+    :tags: bug, tests
+    :tickets: 408
+
+    Fixed test suite to not rely upon ancient "future division" statement to
+    test the :paramref:`.Template.future_imports` feature.   The test is
+    replaced with one that tests only the rendering, not the ultimate effect.

mako/template.py

@@ -119,11 +119,7 @@ class Template:
     :param future_imports: String list of names to import from `__future__`.
      These will be concatenated into a comma-separated string and inserted
      into the beginning of the template, e.g. ``futures_imports=['FOO',
-     'BAR']`` results in ``from __future__ import FOO, BAR``.  If you're
-     interested in using features like the new division operator, you must
-     use future_imports to convey that to the renderer, as otherwise the
-     import will not appear as the first executed statement in the generated
-     code and will therefore not have the desired effect.
+     'BAR']`` results in ``from __future__ import FOO, BAR``.
 
     :param include_error_handler: An error handler that runs when this template
      is included within another one via the ``<%include>`` tag, and raises an

test/test_template.py

@@ -1775,8 +1775,8 @@ def test_via_lookup(self):
 
 class FuturesTest(TemplateTest):
     def test_future_import(self):
-        t = Template("${ x / y }", future_imports=["division"])
-        assert result_lines(t.render(x=12, y=5)) == ["2.4"]
+        t = Template("foobar", future_imports=["annotations"])
+        assert t.code.startswith("from __future__ import annotations")
 
 
 class EscapeTest(TemplateTest):