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I'm signed the CLA

Oh, ignore my comment, I missed the Python version (2.7): in Python 2.7, socket.socket doesn't support the context manager protocol :-(

Ok, I did

Should there be an issue in the bug tracker for this?

Also, I'm applying the cherry-pick for 2.7 label here to make it more obvious that this is for 2.7 branch :)

You can use contextlib.closing().

Thank you @J0l-lnny for your fix! I merged your PR.

@serhiy-storchaka: "LGTM. I think we can ignore very small issue in retrlines() in 2.7."

Right, thank you for your review. If someone wants to handle the most complex corner cases, I suggest to focus on the master branch. Right now, the master branch uses a "nested" with which isn't ideal since it doesn't handle exceptions in creating fp fails (or is interrupted by CTRL+c or whatever):

Extract of ftplib.py in the master branch:

    def retrlines(self, cmd, callback = None):
        ...
        with self.transfercmd(cmd) as conn, \
                 conn.makefile('r', encoding=self.encoding) as fp:
        ...

At least, it ensures that conn and fp are closed properly, right?

What is wrong with a nested with? The resources management in the master branch looks correct to me.

What is wrong with a nested with? The resources management in the master branch looks correct to me.

If makefile() raises an exception, conn is not closed. Well, in fact I'm not sure, that's why I was asking :-)

It is properly closed.

with a, b:
        ...

is just a syntax sugar for

with a:
    with b:
        ...

You perhaps missed with deprecated and removed

with contextlib.nested(a, b):
        ...