Unit test unicode decode on command output, fixes #857

Also fixes stderr/stdout writing refs #743.

buildozer/__init__.py

@@ -327,7 +327,7 @@ def cmd(self, command, **kwargs):
                     ret_stdout.append(chunk)
                 if show_output:
                     if IS_PY3:
-                        stderr.write(chunk.decode('utf-8', 'replace'))
+                        stdout.write(chunk.decode('utf-8', 'replace'))
                     else:
                         stdout.write(chunk)
             if fd_stderr in readx:

tests/test_buildozer.py

@@ -4,7 +4,7 @@
 import mock
 import unittest
 import buildozer as buildozer_module
-from buildozer import Buildozer
+from buildozer import Buildozer, IS_PY3
 from six import StringIO
 import tempfile
 
@@ -158,3 +158,45 @@ def test_android_ant_path(self):
         with mock.patch.object(Buildozer, 'file_exists', return_value=True):
             ant_path = target._install_apache_ant()
             assert ant_path == my_ant_path
+
+    def test_cmd_unicode_decode(self):
+        """
+        Verifies Buildozer.cmd() can properly handle non-unicode outputs.
+        refs: https://github.com/kivy/buildozer/issues/857
+        """
+        buildozer = Buildozer()
+        command = 'uname'
+        kwargs = {
+            'show_output': True,
+            'get_stdout': True,
+            'get_stderr': True,
+        }
+        command_output = b'\x80 cannot decode \x80'
+        # showing the point that we can't decode it
+        with self.assertRaises(UnicodeDecodeError):
+            command_output.decode('utf-8')
+        with mock.patch('buildozer.Popen') as m_popen, \
+                mock.patch('buildozer.select') as m_select, \
+                mock.patch('buildozer.stdout') as m_stdout:
+            m_select.select().__getitem__.return_value = [0]
+            # makes sure fcntl.fcntl() gets what it expects so it doesn't crash
+            m_popen().stdout.fileno.return_value = 0
+            m_popen().stderr.fileno.return_value = 2
+            # Buildozer.cmd() is iterating through command output "chunk" until
+            # one chunk is None
+            m_popen().stdout.read.side_effect = [command_output, None]
+            m_popen().returncode = 0
+            stdout, stderr, returncode = buildozer.cmd(command, **kwargs)
+        # when get_stdout is True, the command output also gets returned
+        assert stdout == command_output.decode('utf-8', 'ignore')
+        assert stderr is None
+        assert returncode == 0
+        # Python2 and Python3 have different approaches for decoding the output
+        if IS_PY3:
+            assert m_stdout.write.call_args_list == [
+                mock.call(command_output.decode('utf-8', 'replace'))
+            ]
+        else:
+            assert m_stdout.write.call_args_list == [
+                mock.call(command_output)
+            ]