Fix encoding error in Python2

Using decode method on subprocess.checkoutput() throws an encoding error
in Python2 when returned value contains non ascii caracters

/reviewed-by @kirr
/reviewed-on !6

rubygems.py

@@ -59,7 +59,7 @@ class Recipe(object):
             env.update(environ)
 
         try:
-            cmd_result = subprocess.check_output(cmd, env=env).decode()
+            return subprocess.check_output(cmd, env=env, universal_newlines=True)
         except OSError as e:
             raise zc.buildout.UserError(
                 'System error, command failed: %s: %s' % (e, cmd))
@@ -75,7 +75,6 @@ class Recipe(object):
                     'System error, command failed with exit code %s: %s' 
                     % (e.returncode, e.cmd)
                 )
-        return cmd_result
 
     def update(self):
         pass

tests/test_data/rubygems_3.1.2_setup_output.txt

+Successfully built RubyGem
+   Name: bundler
+   Version: 2.1.2
+   File: bundler-2.1.2.gem
+ Bundler 2.1.2 installed
+ RubyGems 3.1.2 installed
+ Regenerating binstubs
+ 
+ === 3.1.2 / 2019-12-20
+ 
+ Minor enhancements:
+ 
+ * Restore non prompting `gem update --system` behavior. Pull request #3040
+   by David Rodríguez.
+ * Show only release notes for new code installed. Pull request #3041 by
+   David Rodríguez.
+ * Inform about installed `bundle` executable after `gem update --system`.
+   Pull request #3042 by David Rodríguez.
+ * Use Bundler 2.1.2. Pull request #3043 by SHIBATA Hiroshi.
+ 
+ Bug fixes:
+ 
+ * Require `uri` in source.rb. Pull request #3034 by mihaibuzgau.
+ * Fix `gem update --system --force`. Pull request #3035 by David
+   Rodríguez.
+ * Move `require uri` to source_list. Pull request #3038 by mihaibuzgau.
+ 
+ === 3.1.1 / 2019-12-16
+ 
+ Bug fixes:
+ 
+ * Vendor Bundler 2.1.0 again. The version of Bundler with
+   RubyGems 3.1.0 was Bundler 2.1.0.pre.3. Pull request #3029 by
+   SHIBATA Hiroshi.
+ 
+ 
+ ------------------------------------------------------------------------------
\ No newline at end of file

tests/test_rubygems.py

@@ -271,22 +271,14 @@ class fixture(object):
         shutil.rmtree(str(self.tempdir))
 
 
-class RubyGemsTests(unittest.TestCase):
+class RubyGemsTestCase(unittest.TestCase):
     def check_output_test(self, check_output_mock, expected_arg_list_list):
         self.assertEqual(check_output_mock.call_count,
                           len(expected_arg_list_list))
 
-        for command_nb, expected_arg_list in enumerate(
+        for mock_call, expected_arg_list in zip(check_output_mock.mock_calls,
                                                 expected_arg_list_list):
-            # half of the mock calls come from the use of 'decode' method
-            self.assertEqual(
-                check_output_mock.mock_calls[2*command_nb][1][0],
-                expected_arg_list
-            )
-            self.assertEqual(
-                str(check_output_mock.mock_calls[2*command_nb+1]),
-                'call().decode()'
-            )
+            self.assertEqual(mock_call[1][0], expected_arg_list)
 
     def install_with_default_rubygems_test(self, path, patches,
                                             expected_install_arg_list_list):
@@ -390,7 +382,7 @@ class RubyGemsTests(unittest.TestCase):
         recipe = rubygems.Recipe(buildout, name, options)
         recipe.install()
 
-    @fixture({'recipe': {'gems': 'sass', 'version': '2.0.0'}})
+    @fixture({'recipe': {'gems': 'sass'}, 'version': '2.0.0'})
     def test_version(self, path, patches, buildout, name, options):
         recipe = rubygems.Recipe(buildout, name, options)
         recipe.install()
@@ -434,6 +426,20 @@ class RubyGemsTests(unittest.TestCase):
                 self.assertEqual(matched.group(), '--version=1.0')
                 break
 
+    @fixture({'recipe': {'gems': 'sass'}, 'version': '3.1.2'})
+    def test_non_ascii_encoding(self, path, patches, buildout, name, options):
+        rubygems_setup_output_path = os.path.join(
+            os.path.dirname(os.path.realpath(__file__)),
+            'test_data', 
+            'rubygems_3.1.2_setup_output.txt'
+        )
+        with open(rubygems_setup_output_path) as fd:
+            rubygems_setup_output = fd.read()
+        patches['check_output'].return_value = rubygems_setup_output
+
+        recipe = rubygems.Recipe(buildout, name, options)
+        recipe.install()
+
     @fixture({'recipe': {'gems': 'sass', 'deployment': 'true'}})
     def test_deployment_not_pinned_version_error(
             self, path, patches, buildout, name, options):