PICARD-1207: Fix handling paths with unicode characters on python3

When moving additional files, the call to encode_filename encodes the
path to the original filename converting the variable from str to bytes,
provoking the next exception when calling shutil, which only accepts
strings (the documentation don't specifically mention that for shutil.move,
but it does for copy, copyfile, copymode, etc.)

Traceback (most recent call last):
  File "./picard/util/thread.py", line 47, in run
    result = self.func()
  File "./picard/file.py", line 222, in _save_and_rename
    self._move_additional_files(old_filename, new_filename)
  File "./picard/file.py", line 435, in _move_additional_files
    shutil.move(old_file, new_file)
  File "/usr/x86_64-pc-linux-gnu/lib/python3.6/shutil.py", line 551, in move
    if _destinsrc(src, dst):
  File "/usr/x86_64-pc-linux-gnu/lib/python3.6/shutil.py", line 565, in _destinsrc
    if not src.endswith(os.path.sep):
TypeError: endswith first arg must be bytes or a tuple of bytes, not str

Also, other functions like os.path.dirname, os.path.isdir, os.stat,
os.utime ... allow to be passed a string, instead of the encoded path in
a bytes variable. So I removed the use of encode_filename for all cases
that either require or allow a string to be passed so we don't do
unnecessary processing neither.

I checked this fixes PICARD-1207.

picard/file.py

@@ -206,12 +206,11 @@ class File(QtCore.QObject, Item):
             return None
         new_filename = old_filename
         if not config.setting["dont_write_tags"]:
-            encoded_old_filename = encode_filename(old_filename)
-            info = os.stat(encoded_old_filename)
+            info = os.stat(old_filename)
             self._save(old_filename, metadata)
             if config.setting["preserve_timestamps"]:
                 try:
-                    os.utime(encoded_old_filename, (info.st_atime, info.st_mtime))
+                    os.utime(old_filename, (info.st_atime, info.st_mtime))
                 except OSError:
                     log.warning("Couldn't preserve timestamp for %r", old_filename)
         # Rename files
@@ -222,7 +221,7 @@ class File(QtCore.QObject, Item):
             self._move_additional_files(old_filename, new_filename)
         # Delete empty directories
         if config.setting["delete_empty_dirs"]:
-            dirname = encode_filename(os.path.dirname(old_filename))
+            dirname = os.path.dirname(old_filename)
             try:
                 self._rmdir(dirname)
                 head, tail = os.path.split(dirname)
@@ -380,17 +379,17 @@ class File(QtCore.QObject, Item):
             return old_filename
 
         new_dirname = os.path.dirname(new_filename)
-        if not os.path.isdir(encode_filename(new_dirname)):
+        if not os.path.isdir(new_dirname):
             os.makedirs(new_dirname)
         tmp_filename = new_filename
         i = 1
         while (not pathcmp(old_filename, new_filename + ext) and
-               os.path.exists(encode_filename(new_filename + ext))):
+               os.path.exists(new_filename + ext)):
             new_filename = "%s (%d)" % (tmp_filename, i)
             i += 1
         new_filename = new_filename + ext
         log.debug("Moving file %r => %r", old_filename, new_filename)
-        shutil.move(encode_filename(old_filename), encode_filename(new_filename))
+        shutil.move(old_filename, new_filename)
         return new_filename
 
     def _save_images(self, dirname, metadata):
@@ -408,18 +407,18 @@ class File(QtCore.QObject, Item):
 
     def _move_additional_files(self, old_filename, new_filename):
         """Move extra files, like playlists..."""
-        old_path = encode_filename(os.path.dirname(old_filename))
-        new_path = encode_filename(os.path.dirname(new_filename))
-        patterns = encode_filename(config.setting["move_additional_files_pattern"])
+        old_path = os.path.dirname(old_filename)
+        new_path = os.path.dirname(new_filename)
+        patterns = config.setting["move_additional_files_pattern"]
         patterns = [string_(p.strip()) for p in patterns.split() if p.strip()]
         try:
-            names = list(map(encode_filename, os.listdir(old_path)))
+            names = os.listdir(old_path)
         except os.error:
             log.error("Error: {} directory not found".naming_format(old_path))
             return
         filtered_names = [name for name in names if name[0] != "."]
         for pattern in patterns:
-            pattern_regex = re.compile(encode_filename(fnmatch.translate(pattern)), re.IGNORECASE)
+            pattern_regex = re.compile(fnmatch.translate(pattern), re.IGNORECASE)
             file_names = names
             if pattern[0] != '.':
                 file_names = filtered_names