add additional rewritemeta test for yml

tests/rewritemeta.TestCase

@@ -45,8 +45,7 @@ class RewriteMetaTest(unittest.TestCase):
 
     def test_rewrite_scenario_trivial(self):
 
-        sys.argv.append('a')
-        sys.argv.append('b')
+        sys.argv = ['rewritemeta', 'a', 'b']
 
         with tempfile.TemporaryDirectory() as tmpdir, TmpCwd(tmpdir):
             os.mkdir('metadata')
@@ -81,15 +80,9 @@ class RewriteMetaTest(unittest.TestCase):
                     UpdateCheckMode: None
                     '''))
 
-        # cleanup argv
-        sys.argv.remove('b')
-        sys.argv.remove('a')
-
     def test_rewrite_scenario_txt_to_yml(self):
 
-        sys.argv.append('--to')
-        sys.argv.append('yml')
-        sys.argv.append('a')
+        sys.argv = ['rewritemeta', '--to', 'yml', 'a']
 
         with tempfile.TemporaryDirectory() as tmpdir, TmpCwd(tmpdir):
             os.mkdir('metadata')
@@ -108,15 +101,9 @@ class RewriteMetaTest(unittest.TestCase):
                     UpdateCheckMode: None
                     '''))
 
-        sys.argv.remove('a')
-        sys.argv.remove('yml')
-        sys.argv.remove('--to')
-
     def test_rewrite_scenario_txt_to_yml_no_ruamel(self):
 
-        sys.argv.append('--to')
-        sys.argv.append('yml')
-        sys.argv.append('a')
+        sys.argv = ['rewritemeta', '--to', 'yml', 'a']
 
         with tempfile.TemporaryDirectory() as tmpdir, TmpCwd(tmpdir):
             os.mkdir('metadata')
@@ -134,9 +121,23 @@ class RewriteMetaTest(unittest.TestCase):
                 self.assertEqual(f.read(), textwrap.dedent('''\
                     Auto Name:a'''))
 
-        sys.argv.remove('a')
-        sys.argv.remove('yml')
-        sys.argv.remove('--to')
+    def test_rewrite_scenario_yml_no_ruamel(self):
+        sys.argv = ['rewritemeta', 'a']
+        with tempfile.TemporaryDirectory() as tmpdir, TmpCwd(tmpdir):
+            os.mkdir('metadata')
+            with open('metadata/a.yml', 'w') as f:
+                f.write('AutoName: a')
+
+            def boom(mf, app):
+                raise FDroidException()
+
+            with mock.patch('fdroidserver.metadata.write_yaml', boom):
+                with self.assertRaises(FDroidException):
+                    rewritemeta.main()
+
+            with open('metadata/a.yml') as f:
+                self.assertEqual(f.read(), textwrap.dedent('''\
+                    AutoName: a'''))
 
 
 if __name__ == "__main__":