subp: make ProcessExecutionError have expected types in stderr, stdout.

When subp raised a ProcessExecutionError, that exception's stderr and
stdout might end up being the string '-' rather than bytes.

This mean that:
   try:
       subp(mycommand, decode=False)
   except ProcessExecutionError as e:
       pass

Would have 'e.stdout' set to '-' while the caller would expect bytes.

Also reduce the try/except block in subp to a specifically the two lines
that may raise an OSError.

1 files changed, 15 insertions, 0 deletions

diff --git a/tests/unittests/test_util.py b/tests/unittests/test_util.py
index d63b760e..4a92e741 100644
--- a/tests/unittests/test_util.py
+++ b/tests/unittests/test_util.py
@@ -623,6 +623,7 @@ class TestSubp(helpers.CiTestCase):
     utf8_valid = b'start \xc3\xa9 end'
     utf8_valid_2 = b'd\xc3\xa9j\xc8\xa7'
     printenv = [BASH, '-c', 'for n in "$@"; do echo "$n=${!n}"; done', '--']
+    bogus_command = 'this-is-not-expected-to-be-a-program-name'
 
     def printf_cmd(self, *args):
         # bash's printf supports \xaa.  So does /usr/bin/printf
@@ -712,6 +713,20 @@ class TestSubp(helpers.CiTestCase):
         self.assertIsNone(err)
         self.assertIsNone(out)
 
+    def test_exception_has_out_err_are_bytes_if_decode_false(self):
+        """Raised exc should have stderr, stdout as bytes if no decode."""
+        with self.assertRaises(util.ProcessExecutionError) as cm:
+            util.subp([self.bogus_command], decode=False)
+        self.assertTrue(isinstance(cm.exception.stdout, bytes))
+        self.assertTrue(isinstance(cm.exception.stderr, bytes))
+
+    def test_exception_has_out_err_are_bytes_if_decode_true(self):
+        """Raised exc should have stderr, stdout as string if no decode."""
+        with self.assertRaises(util.ProcessExecutionError) as cm:
+            util.subp([self.bogus_command], decode=True)
+        self.assertTrue(isinstance(cm.exception.stdout, six.string_types))
+        self.assertTrue(isinstance(cm.exception.stderr, six.string_types))
+
     def test_bunch_of_slashes_in_path(self):
         self.assertEqual("/target/my/path/",
                          util.target_path("/target/", "//my/path/"))