Replace deprecated oslo_utils.timeutils.isotime

The isotime method in oslo_utils.timeutils module was deprecated long
ago[1], and remaining usage of the deprecated method causes
DeprecationWarning[2].
This change replaces the deprecated method by a new method implemented
as part of utility methods.

[1] 5cad113739fa906c3901e530fcbfdee3b48961c1

[2] DeprecationWarning: Using function/method 'isotime()' is deprecated
    in version '1.6' and will be removed in a future version: use
    datetime.datetime.isoformat()

Change-Id: I2371e66d84ce8226700d32c90c0730b7c7e607a0

ceilometer/polling/dynamic_pollster.py

@@ -21,13 +21,13 @@ import copy
 import re
 
 from oslo_log import log
-from oslo_utils import timeutils
 
 from requests import RequestException
 
 from ceilometer import declarative
 from ceilometer.polling import plugin_base
 from ceilometer import sample as ceilometer_sample
+from ceilometer import utils as ceilometer_utils
 
 from functools import reduce
 import operator
@@ -123,7 +123,7 @@ class PollsterSampleExtractor(object):
         self.generate_new_metadata_fields(
             metadata=metadata, pollster_definitions=pollster_definitions)
         return ceilometer_sample.Sample(
-            timestamp=timeutils.isotime(),
+            timestamp=ceilometer_utils.isotime(),
             name=pollster_definitions['name'],
             type=pollster_definitions['sample_type'],
             unit=pollster_definitions['unit'],

ceilometer/utils.py

@@ -21,6 +21,7 @@
 import threading
 
 from oslo_config import cfg
+from oslo_utils import timeutils
 
 ROOTWRAP_CONF = "/etc/ceilometer/rootwrap.conf"
 
@@ -47,3 +48,16 @@ def spawn_thread(target, *args, **kwargs):
     t.daemon = True
     t.start()
     return t
+
+
+def isotime(at=None):
+    """Current time as ISO string,
+
+    :returns: Current time in ISO format
+    """
+    if not at:
+        at = timeutils.utcnow()
+    date_string = at.strftime("%Y-%m-%dT%H:%M:%S")
+    tz = at.tzinfo.tzname(None) if at.tzinfo else 'UTC'
+    date_string += ('Z' if tz == 'UTC' else tz)
+    return date_string