Piping and `run_tee` swallows output to sys.stderr of the rear end of piped commands

[simlei]

Take the following constructs:

/tmp/test.py

import plumbum as pb

cmd = (pb.local["/tmp/producer.bash"] | pb.local["/tmp/consumer.bash"])
c,o,e = cmd.run_tee()

/tmp/producer.bash

#!/usr/bin/env bash
echo "PROD: OUT: LINE 1" >/dev/stdout
echo "PROD: OUT: LINE 2" >/dev/stdout
echo "PROD: ERR: LINE 1" >/dev/stderr
echo "PROD: ERR: LINE 2" >/dev/stderr

/tmp/consumer.bash

#!/usr/bin/env bash
while read -r line; do
    echo "STDERR: line read: $line" >/dev/stderr
    echo "STDOUT: line read: $line" >/dev/stdout
done

and execute

python /tmp/test.py
The output is:

STDOUT: line read: PROD: OUT: LINE 1
STDOUT: line read: PROD: OUT: LINE 2
PROD: ERR: LINE 1
PROD: ERR: LINE 2

However, my expectation would be:

PROD: ERR: LINE 1
PROD: ERR: LINE 2
STDERR: line read: PROD: OUT: LINE 1
STDOUT: line read: PROD: OUT: LINE 1
STDERR: line read: PROD: OUT: LINE 2
STDOUT: line read: PROD: OUT: LINE 2

The STDERR: line read... outputs of the rear of the pipe are swallowed somehow.

[rad-pat]

Also experiencing similar where stderr output is missing. Running command below fails and outputs message Could not convert '\\' to a single ASCII character. This works fine when ran as an individual local, but when output is to be piped to next command, the error message is not seen in stderr.

qsv input --escape '\\' '/some_file.csv'

E.g.

# works
chain = qsv['input', '--escape', '\\\\', input_file]
try:
    chain()
except ProcessExecutionError as e:
    print(e.stderr)

# Not working
chain = qsv['input', '--escape', '\\\\', input_file]
chain = chain | qsv['replace', '\\\\000', '', '--not-one']
try:
    chain()
except ProcessExecutionError as e:
    print(e.stderr)