Specifically, the list I've currently found in .py files:

- _pyio.py:

    ValueError("flush of closed file")
    ValueError("flush of closed file")

"of" -> "on" for both.

- configparser.py:

    ValueError("Required argument `source' not given.")
    ValueError("Cannot specify both `filename' and `source'. "

fix ` on the quotes on argument names.

- windows_utils.py

    ValueError("I/O operatioon on closed pipe")

"operatioon" -> "operation"

- proactor_events.py, asynchat.py:

    TypeError('data argument must be byte-ish (%r)',
    raise TypeError('data argument must be byte-ish (%r)',

AFAIK, "byte-ish" isn't used elsewhere, the author probably mean to go for "bytes-like object".

- _header_value_parser.py:

    errors.HeaderParseError("expected atom at a start of "

"at a start of " -> "at the start of "

- http/cookiejar.py:

    raise ValueError("filename must be string-like")
    
I think "must be a str" was intended.

Do you want to create a pull request?

Sure, Serhiy, I'll make a PR in a bit.