Using Copy.rows breaks Connection context manager

[benesch]

Using the awesome new Copy.rows method works great while the COPY operation is running, but appears to leave the connection in an unclean state. Attempting to run another query on the connection, or exit the context manager for the connection, results in "sending query failed: another command is already in progress".

$ cat repro.py
from psycopg3.oids import builtins
import psycopg3

with psycopg3.connect() as conn:
    with conn.cursor() as cur:
        with cur.copy("COPY (VALUES (1), (2), (3)) TO STDOUT (FORMAT BINARY)") as copy:
            copy.set_types([builtins["int4"].oid])
            for row in copy.rows():
                print(row)

$ python repro.py 
(1,)
(2,)
(3,)
Traceback (most recent call last):
  File "repro.py", line 9, in <module>
    print(row)
  File "/home/benesch/Sites/psycopg3-play/venv/lib/python3.8/site-packages/psycopg3/connection.py", line 435, in __exit__
    self.commit()
  File "/home/benesch/Sites/psycopg3-play/venv/lib/python3.8/site-packages/psycopg3/connection.py", line 465, in commit
    self.wait(self._commit_gen())
  File "/home/benesch/Sites/psycopg3-play/venv/lib/python3.8/site-packages/psycopg3/connection.py", line 510, in wait
    return waiting.wait(gen, self.pgconn.socket, timeout=timeout)
  File "/home/benesch/Sites/psycopg3-play/venv/lib/python3.8/site-packages/psycopg3/waiting.py", line 223, in wait_epoll
    s = next(gen)
  File "/home/benesch/Sites/psycopg3-play/venv/lib/python3.8/site-packages/psycopg3/connection.py", line 380, in _commit_gen
    yield from self._exec_command(b"commit")
  File "/home/benesch/Sites/psycopg3-play/venv/lib/python3.8/site-packages/psycopg3/connection.py", line 346, in _exec_command
    self.pgconn.send_query(command)
  File "/home/benesch/Sites/psycopg3-play/venv/lib/python3.8/site-packages/psycopg3/pq/pq_ctypes.py", line 242, in send_query
    raise PQerror(f"sending query failed: {error_message(self)}")
psycopg3.pq.PQerror: sending query failed: another command is already in progress

[benesch]

Thanks very much! The fix indeed works for us.