QbyteArray().data() is always bytes and does not need to be cast to it

a dbus.ByteArray() can simply be initialized from the QByteArray
directly.

src/calibre/ebooks/__init__.py

@@ -67,7 +67,7 @@ class HTMLRenderer(object):
             buf = QBuffer(ba)
             buf.open(QBuffer.WriteOnly)
             image.save(buf, 'JPEG')
-            self.data = bytes(ba.data())
+            self.data = ba.data()
         except Exception as e:
             self.exception = e
             self.traceback = traceback.format_exc()

src/calibre/ebooks/pdf/render/serialize.py

@@ -464,7 +464,7 @@ class PDFStream(object):
         ba = QByteArray()
         buf = QBuffer(ba)
         image.save(buf, 'jpeg', 94)
-        data = bytes(ba.data())
+        data = ba.data()
 
         if has_alpha:
             soft_mask = self.write_image(tmask, w, h, 8)

src/calibre/gui2/__init__.py

@@ -687,7 +687,7 @@ def pixmap_to_data(pixmap, format='JPEG', quality=None):
     buf = QBuffer(ba)
     buf.open(QBuffer.WriteOnly)
     pixmap.save(buf, format, quality=quality)
-    return bytes(ba.data())
+    return ba.data()
 
 
 def decouple(prefix):

src/calibre/gui2/dbus_export/utils.py

@@ -128,7 +128,7 @@ def icon_to_dbus_menu_icon(icon, size=32):
     buf = QBuffer(ba)
     buf.open(QBuffer.WriteOnly)
     icon.pixmap(32).save(buf, 'PNG')
-    return dbus.ByteArray(bytes((ba.data())))
+    return dbus.ByteArray(ba)
 
 
 def setup_for_cli_run():

src/calibre/gui2/library/alternate_views.py

@@ -76,7 +76,7 @@ def image_to_data(image):  # {{{
     buf.open(QBuffer.WriteOnly)
     if not image.save(buf, CACHE_FORMAT):
         raise EncodeError('Failed to encode thumbnail')
-    ret = bytes(ba.data())
+    ret = ba.data()
     buf.close()
     return ret
 # }}}

src/calibre/utils/wmf/__init__.py

@@ -68,4 +68,4 @@ def to_png(bmp):
     buf = QBuffer(ba)
     buf.open(QBuffer.WriteOnly)
     i.save(buf, 'png')
-    return bytes(ba.data())
+    return ba.data()