Use subprocess.Popen to communicate with d8

tools/gypv8sh.py

Index: tools/gypv8sh.py
diff --git a/tools/gypv8sh.py b/tools/gypv8sh.py
index b8bd4066ec28ae2a5b5b9a33e5a2e36e0ceff14b..cb98f4cb6b88101451e0857fc776d9f2ba21fc1e 100755
--- a/tools/gypv8sh.py
+++ b/tools/gypv8sh.py
@@ -44,13 +44,15 @@ def main ():
     print cmd
   if not opts.impotent:
     try:
-      with open(cxxoutfile, 'w') as f:
-        subprocess.check_call(cmd, stdin=subprocess.PIPE, stdout=f)
+      p = subprocess.Popen(cmd, stdout=subprocess.PIPE, bufsize=0)
+      out, err = p.communicate()
+      if p.returncode:
+        raise Exception('Failed to run d8', out, err)
+      with open(cxxoutfile, 'wb') as f:
+        f.write(out)
       shutil.copyfile(inputfile, jsoutfile)
     except Exception, ex:
       if os.path.exists(cxxoutfile):
-        # The contents of the output file will include the error message.
-        print open(cxxoutfile).read()
         os.remove(cxxoutfile)
       if os.path.exists(jsoutfile):
         os.remove(jsoutfile)