cmd = ''.join(['%s ' % c for c in commands])
proc = subprocess.Popen(
    cmd,
    shell=True,
    stdout=subprocess.PIPE,
    stdin=subprocess.PIPE,
    stderr=subprocess.STDOUT,
    universal_newlines=False,
    ).stdout

fse = sys.getfilesystemencoding()
cmd = ''.join(['%s ' % c.encode(fse) if isinstance(c, unicode) else c for c in commands])
proc = subprocess.Popen(
    cmd,
    shell=True,
    stdout=subprocess.PIPE,
    stdin=subprocess.PIPE,
    stderr=subprocess.STDOUT,
    universal_newlines=False,
    ).stdout

#!/usr/bin/env python
# coding: utf-8
  
import subprocess as subp
  
p = subp.Popen([u'echo', u'x', u'б'], stdout=subp.PIPE)
p.wait()
print (p.stdout.read(), p.returncode)

('x \xd0\xb1\n', 0)

Traceback (most recent call last):
  File "d:\test.py", line 6, in <module>
    p = subp.Popen([u'echo', u'x', u'¦-'], stdout=subp.PIPE)
  File "C:\OSGEO4~1\apps\Python27\lib\subprocess.py", line 711, in __init__ errread, errwrite)
  File "C:\OSGEO4~1\apps\Python27\lib\subprocess.py", line 948, in _execute_child startupinfo)
UnicodeEncodeError: 'ascii' codec can't encode character u'\u0431' in position 7: ordinal not in range(128)

import os
 
with os.popen('echo x б') as p:
    print p.read()

import os
 
with os.popen('echo x б') as p:
    print p.read().decode('cp866')

#!/usr/bin/env python
# coding: utf-8
  
import subprocess
 
 
proc = subprocess.Popen(['echo', 'д'], shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out = ' '
while out:
    out = proc.stdout.readline()
    print(out.rstrip().decode('cp866'))