rename stderr_write_bytes, include optional flush

graphviz/_compat.py

@@ -20,8 +20,10 @@ def makedirs(name, mode=0o777, exist_ok=False):
             if not exist_ok or not os.path.isdir(name):
                 raise
 
-    def stderr_write_binary(data):
+    def stderr_write_bytes(data, flush=False):
         sys.stderr.write(data)
+        if flush:
+            sys.stderr.flush()
 
 
 else:
@@ -34,6 +36,8 @@ def iteritems(d):
     def makedirs(name, mode=0o777, exist_ok=False):  # allow os.makedirs mocking
         return os.makedirs(name, mode, exist_ok=exist_ok)
 
-    def stderr_write_binary(data):
+    def stderr_write_bytes(data, flush=False):
         encoding = sys.stderr.encoding or sys.getdefaultencoding()
         sys.stderr.write(data.decode(encoding))
+        if flush:
+            sys.stderr.flush()

graphviz/backend.py

@@ -9,7 +9,7 @@
 import subprocess
 import contextlib
 
-from ._compat import stderr_write_binary
+from ._compat import stderr_write_bytes
 
 from . import tools
 
@@ -167,8 +167,7 @@ def pipe(engine, format, data, quiet=False):
     out, err = proc.communicate(data)
     if proc.returncode:
         if not quiet:
-            stderr_write_binary(err)
-            sys.stderr.flush()
+            stderr_write_bytes(err, flush=True)
         raise subprocess.CalledProcessError(proc.returncode, cmd, output=out)
 
     return out