remove old Python: remove util.text_string

This was a helper for situations when Python 2 and 3 APIs returned bytes
and unicode, respectively. In these situation, we should nowadays know
which of the two we receive, so there's no need to wrap & hide the
`bytes.decode()` anymore (when it is still required).

Detailed justification:

beets/ui/__init__.py:
- command line options are always parsed to str

beets/ui/commands.py:
- confuse's config.dump always returns str
- open(...) defaults to text mode, read()ing str

beetsplug/keyfinder.py:
- ...

beetsplug/web/__init__.py:
- internally, paths are always bytestrings
- additionally, I took the liberty to slighlty re-arrange the code: it
  makes sense to split off the basename first, since we're only
  interested in the unicode conversion of that part.

test/helper.py:
- capture_stdout() gives a StringIO, which yields str

test/test_ui.py:
- self.io, from _common.TestCase, ultimately contains a
  _common.DummyOut, which appears to be dealing with str (cf.
  DummyOut.get)

beets/ui/__init__.py

@@ -790,9 +790,6 @@ def _store_dict(option, opt_str, value, parser):
         setattr(parser.values, dest, {})
         option_values = getattr(parser.values, dest)
 
-    # Decode the argument using the platform's argument encoding.
-    value = util.text_string(value, util.arg_encoding())
-
     try:
         key, value = value.split('=', 1)
         if not (key and value):

beets/ui/commands.py

@@ -1778,7 +1778,7 @@ def config_func(lib, opts, args):
     else:
         config_out = config.dump(full=opts.defaults, redact=opts.redact)
         if config_out.strip() != '{}':
-            print_(util.text_string(config_out))
+            print_(config_out)
         else:
             print("Empty configuration")
 
@@ -1852,7 +1852,7 @@ def completion_script(commands):
     """
     base_script = os.path.join(os.path.dirname(__file__), 'completion_base.sh')
     with open(base_script) as base_script:
-        yield util.text_string(base_script.read())
+        yield base_script.read()
 
     options = {}
     aliases = {}

beets/util/__init__.py

@@ -770,19 +770,6 @@ def as_string(value):
         return str(value)
 
 
-def text_string(value, encoding='utf-8'):
-    """Convert a string, which can either be bytes or unicode, to
-    unicode.
-
-    Text (unicode) is left untouched; bytes are decoded. This is useful
-    to convert from a "native string" (bytes on Python 2, str on Python
-    3) to a consistently unicode value.
-    """
-    if isinstance(value, bytes):
-        return value.decode(encoding)
-    return value
-
-
 def plurality(objs):
     """Given a sequence of hashble objects, returns the object that
     is most common in the set and the its number of appearance. The

beetsplug/keyfinder.py

@@ -77,7 +77,7 @@ class KeyFinderPlugin(BeetsPlugin):
                 continue
 
             try:
-                key = util.text_string(key_raw)
+                key = key_raw.decode("utf-8")
             except UnicodeDecodeError:
                 self._log.error('output is invalid UTF-8')
                 continue

beetsplug/web/__init__.py

@@ -320,9 +320,9 @@ def item_file(item_id):
 
     try:
         # Imitate http.server behaviour
-        unicode_base_filename.encode("latin-1", "strict")
+        base_filename.encode("latin-1", "strict")
     except UnicodeError:
-        safe_filename = unidecode(unicode_base_filename)
+        safe_filename = unidecode(base_filename)
     else:
         safe_filename = unicode_base_filename
 

test/helper.py

@@ -453,7 +453,7 @@ class TestHelper:
     def run_with_output(self, *args):
         with capture_stdout() as out:
             self.run_command(*args)
-        return util.text_string(out.getvalue())
+        return out.getvalue()
 
     # Safe file operations
 

test/test_ui.py

@@ -1163,8 +1163,7 @@ class ShowChangeTest(_common.TestCase):
             cur_album,
             autotag.AlbumMatch(album_dist, info, mapping, set(), set()),
         )
-        # FIXME decoding shouldn't be done here
+        return self.io.getoutput().lower()
-        return util.text_string(self.io.getoutput().lower())
 
     def test_null_change(self):
         msg = self._show_change()