py3: make setup.py gui work

Apparently compileUi explicitly opens the file/buffer as unicode, not
bytes, and then writes a unicode header string (containing the source
file). So the previous attempt to use BytesIO was wrong in this case.

Also images.qrc is being constructed completely in the right here and
now from a bunch of unicode strings, so just use exactly that.

setup/gui.py

@@ -58,7 +58,7 @@ class GUI(Command):
                 for s in sources:
                     files.append('<file>%s</file>'%s)
                 manifest = '<RCC>\n<qresource prefix="/">\n%s\n</qresource>\n</RCC>'%'\n'.join(sorted(files))
-                with open('images.qrc', 'wb') as f:
+                with open('images.qrc', 'w') as f:
                     f.write(manifest)
         finally:
             os.chdir(cwd)

src/calibre/gui2/__init__.py

@@ -1288,7 +1288,7 @@ def build_forms(srcdir, info=None, summary=False, check_for_migration=False):
         if force_compile or not os.path.exists(compiled_form) or os.stat(form).st_mtime > os.stat(compiled_form).st_mtime:
             if not summary:
                 info('\tCompiling form', form)
-            buf = io.BytesIO()
+            buf = io.StringIO()
             compileUi(form, buf)
             dat = buf.getvalue()
             dat = dat.replace('import images_rc', '')
@@ -1298,7 +1298,7 @@ def build_forms(srcdir, info=None, summary=False, check_for_migration=False):
             dat = dat.replace('_("d MMM yyyy")', '"d MMM yyyy"')
             dat = pat.sub(sub, dat)
 
-            open(compiled_form, 'wb').write(dat)
+            open(compiled_form, 'w').write(dat)
             num += 1
     if num:
         info('Compiled %d forms' % num)