make sure destination dir exist before copying files into it

on_build_finished was operating under the assumption that the
_static directory always exist. This is not a valid assumption if
there are no files there for sphinx to copy prior to the execution
of the 'sphinx_feature_classification.support_matrix' extension.

This patch utilizes the copy_asset() utility to copy files as it
is consistent with other sphinx extensions.

Change-Id: Iba538f7cb595c58a0a401e54edf50dc83c5a72d2

sphinx_feature_classification/support_matrix.py

@@ -21,12 +21,12 @@ It is used via a single directive in the .rst file
 
 from os import path
 import re
-import shutil
 
 from docutils import nodes
 from docutils.parsers import rst
 import six
 from six.moves import configparser
+from sphinx.util.fileutil import copy_asset
 
 KEY_PATTERN = re.compile("[^a-zA-Z0-9_]")
 DRIVER_PREFIX = "driver."
@@ -477,8 +477,8 @@ def on_build_finished(app, exc):
     if exc is None:
         src = path.join(path.abspath(path.dirname(__file__)),
                         'support-matrix.css')
-        dst = path.join(app.outdir, '_static', 'support-matrix.css')
-        shutil.copyfile(src, dst)
+        dst = path.join(app.outdir, '_static')
+        copy_asset(src, dst)
 
 
 def setup(app):

sphinx_feature_classification/tests/test_sphinx_feature_classification.py

@@ -21,6 +21,7 @@ Tests for `sphinx_feature_classification` module.
 import os
 
 import ddt
+import fixtures
 import six
 from six.moves import configparser
 
@@ -72,3 +73,15 @@ class MatrixTestCase(base.TestCase):
         fake_implementation = self.matrix.features[0].implementations[key]
         self.assertEqual(status, fake_implementation.status)
         self.assertEqual(notes, fake_implementation.notes)
+
+    def test_on_build_finished(self):
+
+        class FakeApp(object):
+            outdir = self.useFixture(fixtures.TempDir()).path
+
+        app = FakeApp()
+        exc = None
+        support_matrix.on_build_finished(app, exc)
+        expected_file = os.path.join(
+            app.outdir, '_static', 'support-matrix.css')
+        self.assertTrue(os.path.isfile(expected_file))