wic: decode output of subprocess.communicate

stdeout and stderr content returned by communicate API has different
types in Python 3(bytes) and Python 2(string). Decoding it to 'utf-8'
makes it unicode on both pythons.

Decoded stdout and stderr output to utf-8 to make the code
working under both Python 2 and Python 3.

(From OE-Core rev: 5b556f58a171e3d45107bb56a1f780e5c1abba37)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/utils/runner.py

@@ -65,8 +65,8 @@ def runtool(cmdln_or_args, catch=1):
         process = subprocess.Popen(cmdln_or_args, stdout=sout,
                                    stderr=serr, shell=shell)
         (sout, serr) = process.communicate()
-        # combine stdout and stderr, filter None out
-        out = ''.join(filter(None, [sout, serr]))
+        # combine stdout and stderr, filter None out and decode
+        out = ''.join([out.decode('utf-8') for out in [sout, serr] if out])
     except OSError as err:
         if err.errno == 2:
             # [Errno 2] No such file or directory