[manual] tools: Move check_output into a shared file

We leave the stuff under api/ alone for now, since we need to be able to ship
it as a standalone thing.

tools/post-receive wasn't using the function anyway.

For push to master: Push this commit, update post-receive per instructions at
the top of that file, then push the rest of the branch to confirm that the hook
still works.

No manual instructions for prod.

(imported from commit 9bcbe14c08d15eda47d82f0b702bad33e217a074)

bots/check-rabbitmq-queue

@@ -5,6 +5,11 @@ import subprocess
 import re
 import time
 
+from os import path
+
+sys.path.append(path.join(path.dirname(__file__), '../tools'))
+from humbug_tools import check_output
+
 WARN_THRESHOLD = 100
 CRIT_THRESHOLD = 200
 
@@ -15,23 +20,8 @@ states = {
     3: "UNKNOWN"
 }
 
-# check_output is backported from subprocess.py in Python 2.7
-def check_output(*popenargs, **kwargs):
-    if 'stdout' in kwargs:
-        raise ValueError('stdout argument not allowed, it will be overridden.')
-    process = subprocess.Popen(stdout=subprocess.PIPE, *popenargs, **kwargs)
-    output, unused_err = process.communicate()
-    retcode = process.poll()
-    if retcode:
-        cmd = kwargs.get("args")
-        if cmd is None:
-            cmd = popenargs[0]
-        raise subprocess.CalledProcessError(retcode, cmd, output=output)
-    return output
-subprocess.check_output = check_output
-
 re = re.compile(r'(\w+)\t(\d+)')
-output = subprocess.check_output(['/usr/sbin/rabbitmqctl', 'list_queues'], shell=False)
+output = check_output(['/usr/sbin/rabbitmqctl', 'list_queues'], shell=False)
 
 status = 0
 max_count = 0