Handle missing nanos.

core/google/cloud/_helpers.py

@@ -53,8 +53,10 @@
     (?P<no_fraction>
         \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}  # YYYY-MM-DDTHH:MM:SS
     )
-    \.                                       # decimal point
-    (?P<nanos>\d{1,9})                       # nanoseconds, maybe truncated
+    (                                        # Optional decimal part
+     \.                                      # decimal point
+     (?P<nanos>\d{1,9})                      # nanoseconds, maybe truncated
+    )?
     Z                                        # Zulu
 """, re.VERBOSE)
 # NOTE: Catching this ImportError is a workaround for GAE not supporting the
@@ -429,9 +431,12 @@ def _rfc3339_nanos_to_datetime(dt_str):
     bare_seconds = datetime.datetime.strptime(
         with_nanos.group('no_fraction'), _RFC3339_NO_FRACTION)
     fraction = with_nanos.group('nanos')
-    scale = 9 - len(fraction)
-    nanos = int(fraction) * (10 ** scale)
-    micros = nanos // 1000
+    if fraction is None:
+        micros = 0
+    else:
+        scale = 9 - len(fraction)
+        nanos = int(fraction) * (10 ** scale)
+        micros = nanos // 1000
     return bare_seconds.replace(microsecond=micros, tzinfo=UTC)
 
 

core/unit_tests/test__helpers.py

@@ -667,6 +667,24 @@ def test_w_truncated_nanos(self):
                 year, month, day, hour, minute, seconds, micros, UTC)
             self.assertEqual(result, expected_result)
 
+    def test_without_nanos(self):
+        import datetime
+        from google.cloud._helpers import UTC
+
+        year = 1988
+        month = 4
+        day = 29
+        hour = 12
+        minute = 12
+        seconds = 12
+
+        dt_str = '%d-%02d-%02dT%02d:%02d:%02dZ' % (
+            year, month, day, hour, minute, seconds)
+        result = self._callFUT(dt_str)
+        expected_result = datetime.datetime(
+            year, month, day, hour, minute, seconds, 0, UTC)
+        self.assertEqual(result, expected_result)
+
     def test_w_naonseconds(self):
         import datetime
         from google.cloud._helpers import UTC