Use a polyglot IO class for device debug output

src/calibre/devices/__init__.py

@@ -8,7 +8,6 @@ Device drivers.
 
 import sys, time, pprint
 from functools import partial
-from io import BytesIO
 
 DAY_MAP   = dict(Sun=0, Mon=1, Tue=2, Wed=3, Thu=4, Fri=5, Sat=6)
 MONTH_MAP = dict(Jan=1, Feb=2, Mar=3, Apr=4, May=5, Jun=6, Jul=7, Aug=8, Sep=9, Oct=10, Nov=11, Dec=12)
@@ -74,10 +73,11 @@ def debug(ioreg_to_tmp=False, buf=None, plugins=None,
     from calibre.devices.scanner import DeviceScanner
     from calibre.constants import iswindows, isosx
     from calibre import prints
+    from polyglot.io import PolyglotBytesIO
     oldo, olde = sys.stdout, sys.stderr
 
     if buf is None:
-        buf = BytesIO()
+        buf = PolyglotBytesIO()
     sys.stdout = sys.stderr = buf
     out = partial(prints, file=buf)
 

src/calibre/gui2/__init__.py

@@ -1264,8 +1264,9 @@ def form_to_compiled_form(form):
 
 
 def build_forms(srcdir, info=None, summary=False, check_for_migration=False):
-    import re, io
+    import re
     from PyQt5.uic import compileUi
+    from polyglot.io import PolyglotStringIO
     forms = find_forms(srcdir)
     if info is None:
         from calibre import prints
@@ -1284,13 +1285,6 @@ def build_forms(srcdir, info=None, summary=False, check_for_migration=False):
     # the qt5 migration
     force_compile = check_for_migration and not gprefs.get('migrated_forms_to_qt5', False)
 
-    class PolyglotStringIO(io.StringIO):
-
-        def write(self, x):
-            if isinstance(x, bytes):
-                x = x.decode('utf-8')
-            io.StringIO.write(self, x)
-
     for form in forms:
         compiled_form = form_to_compiled_form(form)
         if force_compile or not os.path.exists(compiled_form) or os.stat(form).st_mtime > os.stat(compiled_form).st_mtime:

src/polyglot/io.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python2
+# vim:fileencoding=utf-8
+# License: GPL v3 Copyright: 2019, Kovid Goyal <kovid at kovidgoyal.net>
+
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from io import StringIO, BytesIO
+
+
+class PolyglotStringIO(StringIO):
+
+    def __init__(self, initial_data=None, encoding='utf-8'):
+        StringIO.__init__(self)
+        self._encoding_for_bytes = encoding
+        if initial_data is not None:
+            self.write(initial_data)
+
+    def write(self, x):
+        if isinstance(x, bytes):
+            x = x.decode(self._encoding_for_bytes)
+        StringIO.write(self, x)
+
+
+class PolyglotBytesIO(BytesIO):
+
+    def __init__(self, initial_data=None, encoding='utf-8'):
+        BytesIO.__init__(self)
+        self._encoding_for_bytes = encoding
+        if initial_data is not None:
+            self.write(initial_data)
+
+    def write(self, x):
+        if not isinstance(x, bytes):
+            x = x.encode(self._encoding_for_bytes)
+        BytesIO.write(self, x)