Merge fix for handling of stderr/stdout on pythonw.

NEWS

@@ -1,5 +1,10 @@
 0.19.7	UNRELEASED
 
+ BUG FIXES
+
+  * Don't write to stdout and stderr when they are not available
+    (such as is the case for pythonw). (Sylvia van Os, #652)
+
 0.19.6	2018-08-11
 
  BUG FIXES

appveyor.yml

@@ -84,6 +84,7 @@ build_script:
 
 test_script:
   - "build.cmd %PYTHON%\\python.exe setup.py test"
+  - "build.cmd %PYTHON%\\pythonw.exe setup.py test"
 
 after_test:
   - "build.cmd %PYTHON%\\python.exe setup.py bdist_wheel"

dulwich/porcelain.py

@@ -61,7 +61,7 @@ from contextlib import (
     closing,
     contextmanager,
 )
-from io import BytesIO
+from io import BytesIO, RawIOBase
 import datetime
 import os
 import posixpath
@@ -139,8 +139,27 @@ from dulwich.server import (
 GitStatus = namedtuple('GitStatus', 'staged unstaged untracked')
 
 
-default_bytes_out_stream = getattr(sys.stdout, 'buffer', sys.stdout)
-default_bytes_err_stream = getattr(sys.stderr, 'buffer', sys.stderr)
+class NoneStream(RawIOBase):
+    """Fallback if stdout or stderr are unavailable, does nothing."""
+    def read(self, size=-1):
+        return None
+
+    def readall(self):
+        return None
+
+    def readinto(self, b):
+        return None
+
+    def write(self, b):
+        return None
+
+
+default_bytes_out_stream = getattr(
+        sys.stdout, 'buffer', sys.stdout
+    ) or NoneStream()
+default_bytes_err_stream = getattr(
+        sys.stderr, 'buffer', sys.stderr
+    ) or NoneStream()
 
 
 DEFAULT_ENCODING = 'utf-8'

dulwich/tests/test_porcelain.py

@@ -224,6 +224,20 @@ class CloneTests(PorcelainTestCase):
             self.repo.path, target_path, checkout=True, errstream=errstream)
         r.close()
 
+    def test_no_head_no_checkout_outstream_errstream_autofallback(self):
+        f1_1 = make_object(Blob, data=b'f1')
+        commit_spec = [[1]]
+        trees = {1: [(b'f1', f1_1), (b'f2', f1_1)]}
+
+        (c1, ) = build_commit_graph(self.repo.object_store, commit_spec, trees)
+        self.repo.refs[b"refs/heads/master"] = c1.id
+        target_path = tempfile.mkdtemp()
+        self.addCleanup(shutil.rmtree, target_path)
+        errstream = porcelain.NoneStream()
+        r = porcelain.clone(
+            self.repo.path, target_path, checkout=True, errstream=errstream)
+        r.close()
+
 
 class InitTests(TestCase):