revert some reverts

Author: AlexWaygood

Lib/_collections_abc.py

@@ -1057,6 +1057,7 @@ def count(self, value):
 
 Sequence.register(tuple)
 Sequence.register(str)
+Sequence.register(bytes)
 Sequence.register(range)
 Sequence.register(memoryview)
 
@@ -1159,4 +1160,4 @@ def __iadd__(self, values):
 
 
 MutableSequence.register(list)
-MutableSequence.register(bytearray)  # Multiply inheriting, see ByteString
+MutableSequence.register(bytearray)

Lib/test/libregrtest/refleak.py

@@ -253,7 +253,6 @@ def dash_R_cleanup(fs, ps, pic, zdc, abcs, linecache_data):
         zipimport._zip_directory_cache.update(zdc)
 
     # Clear ABC registries, restoring previously saved ABC registries.
-    # ignore deprecation warning for collections.abc.ByteString
     abs_classes = [getattr(collections.abc, a) for a in collections.abc.__all__]
     abs_classes = filter(isabstract, abs_classes)
     for abc in abs_classes: