I was just looking at documentation of https://docs.python.org/3.6/library/subprocess.html#subprocess.run
and thought that it doesn't support passing `env` because the list of supported keyword arguments is exhaustive (no **kwargs). But it does support passing **kwargs to Popen, so that should be specified in the docs.

But the documentation does say "The arguments shown above are merely the most common ones...The full function signature is largely the same as that of the Popen constructor...", no ?

Yes, but the most prominent thing to indicate that is **kwargs in the actual function signature. And, as far as I'm concerned, lack of **kwargs means the function signature is exhaustive and there's no point in looking for fine print somewhere in the middle of the textual description.

I agree with Xavier's comment, but I've bitten by this before so I think it would be better if we add more common arguments to the subprocess.run() signature.

Adding **kwargs wouldn't be entirely correct since subprocess.run() doesn't pass all its arguments to subprocess.Popen().

Let's add 'env=None' to the signature of subprocess.run():

.. function:: run(args, *, stdin=None, input=None, stdout=None, stderr=None,\
                  shell=False, cwd=None, timeout=None, check=False, \
                  encoding=None, errors=None, text=None)

https://github.com/python/cpython/blob/3055c947f98a078bd10d6a8cc352048a1b771d60/Doc/library/subprocess.rst#using-the-modsubprocess-module

> Let's add 'env=None' to the signature of subprocess.run():

+1

New changeset af1ec97a6d1dde68b2dc0ee9b78965eb219061a8 by Berker Peksag (Tobias Kunze) in branch 'master':
bpo-32392: Document env keyword argument of subprocess.run() (GH-7289)
https://github.com/python/cpython/commit/af1ec97a6d1dde68b2dc0ee9b78965eb219061a8

New changeset 23b7ee205270320f836e93e411b28ac995cbabf1 by Miss Islington (bot) in branch '3.7':
bpo-32392: Document env keyword argument of subprocess.run() (GH-7289)
https://github.com/python/cpython/commit/23b7ee205270320f836e93e411b28ac995cbabf1

New changeset 279564431e8e2fa4c20e8850420caea484a5d20b by Berker Peksag in branch '3.6':
[3.6] bpo-32392: Document env keyword argument of subprocess.run() (GH-7289)
https://github.com/python/cpython/commit/279564431e8e2fa4c20e8850420caea484a5d20b

Thanks!