releasetools: Set default stdout and stderr in common.Run().

stdout and stderr will default to subprocess.PIPE and subprocess.STDOUT
respectively (which is the expected behavior from most of the existing
callers), unless caller specifies any of them.

Test: `m dist`
Test: python -m unittest \
          test_common \
          test_add_img_to_target_files \
          test_ota_from_target_files \
          test_validate_target_files
Change-Id: I43b3f08edfa8a9bcfe54baf9848dc705c048e327

tools/releasetools/blockimgdiff.py

@@ -23,7 +23,6 @@ import multiprocessing
 import os
 import os.path
 import re
-import subprocess
 import sys
 import threading
 from collections import deque, OrderedDict
@@ -43,11 +42,10 @@ def compute_patch(srcfile, tgtfile, imgdiff=False):
 
   # Don't dump the bsdiff/imgdiff commands, which are not useful for the case
   # here, since they contain temp filenames only.
-  p = common.Run(cmd, verbose=False, stdout=subprocess.PIPE,
-                 stderr=subprocess.STDOUT)
-  output, _ = p.communicate()
+  proc = common.Run(cmd, verbose=False)
+  output, _ = proc.communicate()
 
-  if p.returncode != 0:
+  if proc.returncode != 0:
     raise ValueError(output)
 
   with open(patchfile, 'rb') as f:
@@ -1494,9 +1492,9 @@ class BlockImageDiff(object):
                "--block-limit={}".format(max_blocks_per_transfer),
                "--split-info=" + patch_info_file,
                src_file, tgt_file, patch_file]
-        p = common.Run(cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
-        imgdiff_output, _ = p.communicate()
-        assert p.returncode == 0, \
+        proc = common.Run(cmd)
+        imgdiff_output, _ = proc.communicate()
+        assert proc.returncode == 0, \
             "Failed to create imgdiff patch between {} and {}:\n{}".format(
                 src_name, tgt_name, imgdiff_output)