git cl: refactor direct usage of time.sleep and time.time.

git_cl.py

Index: git_cl.py
diff --git a/git_cl.py b/git_cl.py
index d8b90046c27dafb7ca4cf4e15d830c9754450290..18dc963407d46321b7f77937af2f9ed1de3fcfeb 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -23,7 +23,6 @@ import re
 import stat
 import sys
 import textwrap
-import time
 import traceback
 import urllib
 import urllib2
@@ -148,6 +147,13 @@ def BranchExists(branch):
   return not code
 
 
+def time_sleep(seconds):
+  # Use this so that it can be mocked in tests without interfering with python
+  # system machinery.
+  import time  # Local import to discourage others from importing time globally.
+  return time.sleep(seconds)
+
+
 def ask_for_data(prompt):
   try:
     return raw_input(prompt)
@@ -313,7 +319,7 @@ def _buildbucket_retry(operation_name, http, *args, **kwargs):
 
     # status >= 500 means transient failures.
     logging.debug('Transient errors when %s. Will retry.', operation_name)
-    time.sleep(0.5 + 1.5*try_count)
+    time_sleep(0.5 + 1.5*try_count)
     try_count += 1
   assert False, 'unreachable'