Fix support for python3 in download_bower.py

Was getting "TypeError: write() argument must be str, not bytes"

Change-Id: I68ba54f7df1ba4c9ae160442f93a74c837ddc9d3

tools/js/download_bower.py

@@ -46,7 +46,8 @@ def bower_info(bower, name, package, version):
         raise
     out, err = p.communicate()
     if p.returncode:
-        sys.stderr.write(err)
+        # For python3 support we wrap str around err.
+        sys.stderr.write(str(err))
         raise OSError('Command failed: %s' % ' '.join(cmd))
 
     try: