Don't use os.system() in compilemessages.

Fixes #19584.

This implies stop storing file path command line arguments in envvars as
a security measure to start relying on with Popen's shell=False instead,
and addition of an 'utils' module.

Thanks kmichel_wgs for the report.

tests/i18n/commands/compilation.py

@@ -99,3 +99,22 @@ class MultipleLocaleCompilationTests(MessageCompilationTests):
 
         self.assertTrue(os.path.exists(self.MO_FILE_HR))
         self.assertTrue(os.path.exists(self.MO_FILE_FR))
+
+
+class CompilationErrorHandling(MessageCompilationTests):
+
+    LOCALE='ja'
+    MO_FILE='locale/%s/LC_MESSAGES/django.mo' % LOCALE
+
+    def setUp(self):
+        super(CompilationErrorHandling, self).setUp()
+        self.addCleanup(self._rmfile, os.path.join(test_dir, self.MO_FILE))
+
+    def _rmfile(self, filepath):
+        if os.path.exists(filepath):
+            os.remove(filepath)
+
+    def test_error_reported_by_msgfmt(self):
+        os.chdir(test_dir)
+        with self.assertRaises(CommandError):
+            call_command('compilemessages', locale=self.LOCALE, stderr=StringIO())

tests/i18n/commands/locale/ja/LC_MESSAGES/django.po

@@ -0,0 +1,21 @@
+# SOME DESCRIPTIVE TITLE.
+# Copyright (C) YEAR THE PACKAGE'S COPYRIGHT HOLDER
+# This file is distributed under the same license as the PACKAGE package.
+# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: PACKAGE VERSION\n"
+"Report-Msgid-Bugs-To: \n"
+"POT-Creation-Date: 2011-12-04 04:59-0600\n"
+"PO-Revision-Date: 2013-02-26 21:29-0300\n"
+"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+"Language-Team: LANGUAGE <LL@li.org>\n"
+"Language: ja\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=UTF-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+"Plural-Forms: nplurals=1; plural=0;\n"
+
+#, brainfuck-format
+msgwhat!? "This is an invalid PO file. GNU msgfmt should reject it."

tests/i18n/tests.py

@@ -41,7 +41,8 @@ if can_run_extraction_tests:
         MultipleLocaleExtractionTests)
 if can_run_compilation_tests:
     from .commands.compilation import (PoFileTests, PoFileContentsTests,
-        PercentRenderingTests, MultipleLocaleCompilationTests)
+        PercentRenderingTests, MultipleLocaleCompilationTests,
+        CompilationErrorHandling)
 from .contenttypes.tests import ContentTypeTests
 from .forms import I18nForm, SelectDateForm, SelectDateWidget, CompanyForm
 from .models import Company, TestModel