cauacase.{test,ca}: Silence pylint consider-using-with .

Because:
- Non-blocking lock acquisition does not work with a context manager.
- subprocess is not a context manager in python 2.7 .

caucase/ca.py

@@ -508,7 +508,9 @@ class CertificateAuthority(object):
         self._ca_key_pairs_list[-1]['crt'].not_valid_after -
         datetime.datetime.utcnow()
       ).total_seconds() / self._crt_life_time.total_seconds() <= 2
+      # pylint: disable=consider-using-with
       ) and self._ca_renewal_lock.acquire(False):
+      # pylint: enable=consider-using-with
       try:
         # No CA certificate at all or less than 2 certificate validity periods
         # left with latest CA certificate. Prepare the next one so it starts

caucase/test.py

@@ -3790,7 +3790,7 @@ def _runCaucaseSh(*args):
   environ = os.environ.copy()
   environ['CAUCASE_PYTHON'] = sys.executable
   with open(os.devnull, 'rb') as devnull:
-    process = subprocess.Popen(
+    process = subprocess.Popen( # pylint: disable=consider-using-with
       command,
       stdin=devnull,
       stdout=subprocess.PIPE,