[test_unicode_literals] Arm unicode_literals check

From now on, the line

from __future__ import unicode_literals

should be contained in every single Python file lest we run into any more 2.x/3.x issues.
Going forward, we're likely to develop on 3.x only and would likely miss subtle bugs otherwise.

test/test_unicode_literals.py

@@ -9,14 +9,13 @@ rootDir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 
 IGNORED_FILES = [
     'setup.py',  # http://bugs.python.org/issue13943
+    'conf.py',
+    'buildserver.py',
 ]
 
 
 class TestUnicodeLiterals(unittest.TestCase):
     def test_all_files(self):
-        print('Skipping this test (not yet fully implemented)')
-        return
-
         for dirpath, _, filenames in os.walk(rootDir):
             for basename in filenames:
                 if not basename.endswith('.py'):
@@ -30,10 +29,10 @@ class TestUnicodeLiterals(unittest.TestCase):
 
                 if "'" not in code and '"' not in code:
                     continue
-                imps = 'from __future__ import unicode_literals'
-                self.assertTrue(
-                    imps in code,
-                    ' %s  missing in %s' % (imps, fn))
+                self.assertRegexpMatches(
+                    code,
+                    r'(?:#.*\n*)?from __future__ import (?:[a-z_]+,\s*)*unicode_literals',
+                    'unicode_literals import  missing in %s' % fn)
 
                 m = re.search(r'(?<=\s)u[\'"](?!\)|,|$)', code)
                 if m is not None: