UTC ISO8601 from timestamp

Taken from glance xattr.py module. This function converts timestamp
formated dates into a UTC Iso 8601 date. It is being required in
multiple places now (mostly on clients printing dates) in order to make
dates human readable.

Change-Id: I6f19325a4c2df241a0ef76bd256280a2930d9265

openstack/common/timeutils.py

@@ -98,6 +98,11 @@ def utcnow():
     return datetime.datetime.utcnow()
 
 
+def iso8601_from_timestamp(timestamp):
+    """Returns a iso8601 formated date from timestamp"""
+    return isotime(datetime.datetime.utcfromtimestamp(timestamp))
+
+
 utcnow.override_time = None
 
 

tests/unit/test_timeutils.py

@@ -15,6 +15,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import calendar
 import datetime
 import unittest
 
@@ -148,6 +149,12 @@ class TimeUtilsTest(unittest.TestCase):
         self.assertAlmostEquals(604859.123456,
                                 timeutils.delta_seconds(before, after))
 
+    def test_iso8601_from_timestamp(self):
+        utcnow = timeutils.utcnow()
+        iso = timeutils.isotime(utcnow)
+        ts = calendar.timegm(utcnow.timetuple())
+        self.assertEqual(iso, timeutils.iso8601_from_timestamp(ts))
+
 
 class TestIso8601Time(unittest.TestCase):