False positive "no-member" for Python 3 subprocess.Popen().communicate()

[pylint-bot]

Originally reported by: Anonymous

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Pylint assumes that Popen().communicate() returns a tuple of 2 "str" instance, but this is incorrect in Python 3 where it returns a tuple of 2 "bytes" instances, unless universal_newlines=True is passed to Popen, in which case it returns a tuple of 2 "str" instances again.

$ cat subprocess_test.py
from subprocess import Popen, PIPE
stdout, stderr = Popen('/bin/ls', stdout=PIPE).communicate()
print(stdout.decode("ascii"))

$ pylint -d C -r n subprocess_test.py
************* Module subprocess_test
E: 3, 6: Instance of 'str' has no 'decode' member (no-member)

Python 3 runs the code fine.

I wonder if this is related to the "brain" package included in asteroid, as in the asteroid package:

$ grep -A 12 Popen brain/py2stdlib.py
class Popen(object):
returncode = pid = 0
stdin = stdout = stderr = file()

def __init__(self, args, bufsize=0, executable=None,
             stdin=None, stdout=None, stderr=None,
             preexec_fn=None, close_fds=False, shell=False,
             cwd=None, env=None, universal_newlines=False,
             startupinfo=None, creationflags=0):
    pass

def communicate(self, input=None):
    return ('string', 'string')

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• Bitbucket: https://bitbucket.org/logilab/pylint/issue/65

[pylint-bot]

Original comment by Sylvain Thénault (BitBucket: sthenault, GitHub: @sthenault?):

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this should indeed be fixed in the pylint-brain project

[pylint-bot]

Original comment by Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore):

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This is already fixed in pylint-brain and the fix will be included in the next astroid version.

[pylint-bot]

Original comment by Sylvain Thénault (BitBucket: sthenault, GitHub: @sthenault?):

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Removing version: 1.0 (automated comment)