In addition to issue16518. There are other non-fixed messages (may be introduced after 3.3):

>>> b''.join([''])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: sequence item 0: expected bytes, bytearray, or an object with the buffer interface, str found
>>> str(42, 'utf8')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: coercing to str: need bytes, bytearray or buffer-like object, int found
>>> import array; array.array('B').frombytes(array.array('I'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: string/buffer of bytes required.
>>> import socket; print(socket.socket.sendmsg.__doc__)
sendmsg(buffers[, ancdata[, flags[, address]]]) -> count

Send normal and ancillary data to the socket, gathering the
non-ancillary data from a series of buffers and concatenating it into
a single message.  The buffers argument specifies the non-ancillary
data as an iterable of buffer-compatible objects (e.g. bytes objects).
The ancdata argument specifies the ancillary data (control messages)
as an iterable of zero or more tuples (cmsg_level, cmsg_type,
cmsg_data), where cmsg_level and cmsg_type are integers specifying the
protocol level and protocol-specific type respectively, and cmsg_data
is a buffer-compatible object holding the associated data.  The flags
argument defaults to 0 and has the same meaning as for send().  If
address is supplied and not None, it sets a destination address for
the message.  The return value is the number of bytes of non-ancillary
data sent.

And there are several mentions of "buffer-like" or "buffer-compatible" in the documentation.

Here is a patch which fixes remnants. It also corrects descriptions of parsing arguments format units.

Could anyone please look at the patch? It touches only docs and comments.

There's no review link.  And no obvious reason why there isn't.  Could you try regenerating the patch and uploading it again?

Regenerated for review. I don't know why Rietweld didn't like previous patch.

Made some review comments.  The last comment change (deletion) in unicodeobject.c is not as obvious as the other changes were; I'm not familiar enough with the C API to know why it is correct.  I trust you on that, though :)

Thank you David.

I have left enumerations of concrete bytes-like classes (bytes and bytearray) because I thought that it is good to be more verbose in the documentation. I left the decision how write it to you: ":class:`bytes`, :class:`bytearray` or :term:`bytes-like object`", ":term:`bytes-like object` such as :class:`bytes` and :class:`bytearray`", or just ":term:`bytes-like object`".

I don't understand your comment about unicodeobject.c. This change doesn't differ from others. May be you mean unicodeobject.h? Yes, "char buffer" is Python 2 term and doesn't make sense in 3.x.

Yeah, just ignore the unicodeobject.c comment comment.

It seems to me that the stuff in the parens is supposed to be a precise description of what the format code handles, with elaboration in the following text.  So I'd prefer to just use the :term: in those lists.  But like I said I'm not that familiar with the C api, so I'm not sure how much weight my opinion should carry :)  

The biggest thing is consistency.  If you want to keep all of them in the list, I'd favor the "such as" formulation.

New changeset 853e3e115db4 by Serhiy Storchaka in branch '3.4':
Issue #22581: Use more "bytes-like object" throughout the docs and comments.
https://hg.python.org/cpython/rev/853e3e115db4

New changeset 450a025b1669 by Serhiy Storchaka in branch 'default':
Issue #22581: Use more "bytes-like object" throughout the docs and comments.
https://hg.python.org/cpython/rev/450a025b1669

Committed with just "bytes-like object". Thank you David for your review.