Fix test_main and test_depends for systems missing lsb_release

There are a couple of tests that actually end up trying to run lsb_release
on the host. If not present, this causes tests to fail. This just makes sure
subprocess.check_output is suitably mocked out to avoid that.

Change-Id: Ifb8981d6b39b7c52b9e72fdf8d1e5e4566d45472

bindep/tests/test_depends.py

@@ -47,8 +47,9 @@ class TestDepends(TestCase):
         self.assertEqual([], depends.profiles())
 
     def test_platform_profiles_succeeds(self):
-        depends = Depends("")
-        self.assertIsInstance(depends.platform_profiles(), list)
+        with self._mock_lsb('Ubuntu'):
+            depends = Depends("")
+            self.assertIsInstance(depends.platform_profiles(), list)
 
     @contextlib.contextmanager
     def _mock_lsb(self, platform):

bindep/tests/test_main.py

@@ -41,6 +41,9 @@ class MainFixture(Fixture):
         self.path = self.useFixture(TempDir()).path
         self.addCleanup(os.chdir, self.path)
         os.chdir(self.path)
+        fake_lsb = b'Ubuntu\n14.04\nTrusty'
+        self.useFixture(MonkeyPatch('subprocess.check_output',
+                                    lambda *a, **k: fake_lsb))
 
 
 class TestMain(TestCase):