Silence pub --version tests

Silence pub --version tests

BUG=
R=rmacnak@google.com

Committed: https://github.com/dart-lang/sdk/commit/dfe65284007c0df7949cc1db516822b606f23a9b

[Cutch, 2015-09-23 21:12:17]

johnmccutchan@google.com changed reviewers:
+ rmacnak@google.com

[rmacnak, 2015-09-23 21:15:00]

lgtm

[Cutch, 2015-09-23 21:16:08]

Committed patchset #1 (id:1) manually as
dfe65284007c0df7949cc1db516822b606f23a9b (presubmit successful).

[Bob Nystrom, 2015-09-29 16:06:57]

rnystrom@google.com changed reviewers:
+ rnystrom@google.com

[Bob Nystrom, 2015-09-29 16:06:57]

https://codereview.chromium.org/1360283002/diff/1/tools/observatory_tool.py
File tools/observatory_tool.py (right):

https://codereview.chromium.org/1360283002/diff/1/tools/observatory_tool.py#n...
tools/observatory_tool.py:83: options.dart_executable is not None)
Drive-by! Instead of making an explicit null sink, I've used this before:

try:
  subprocess.check_output(args, stderr=subprocess.STDOUT)
except subprocess.CalledProcessError as error:
  ...

check_output consumes and returns stdout. If you redirect stderr to that, it
consumes all output. It raises a CalledProcessError error if the process exits
with a non-zero exit code.