minor: fix build warning and updated the metric proto link

opencensus/metrics/export/metric.py

@@ -19,9 +19,9 @@ class Metric(object):
     """A collection of time series data and label metadata.
 
     This class implements the spec for v1 Metrics as of opencensus-proto
-    release v0.0.2. See opencensus-proto for details:
+    release v0.1.0. See opencensus-proto for details:
 
-    https://github.com/census-instrumentation/opencensus-proto/blob/24333298e36590ea0716598caacc8959fc393c48/src/opencensus/proto/metrics/v1/metrics.proto#33
+    https://github.com/census-instrumentation/opencensus-proto/blob/v0.1.0/src/opencensus/proto/metrics/v1/metrics.proto#L35
 
     Defines a Metric which has one or more timeseries.
 

opencensus/metrics/export/metric_descriptor.py

@@ -38,7 +38,7 @@ class MetricDescriptorType(object):
     MetricDescriptorType is an enum of valid MetricDescriptor type values. See
     opencensus-proto for details:
 
-        https://github.com/census-instrumentation/opencensus-proto/blob/24333298e36590ea0716598caacc8959fc393c48/src/opencensus/proto/metrics/v1/metrics.proto#L73  # noqa
+    https://github.com/census-instrumentation/opencensus-proto/blob/v0.1.0/src/opencensus/proto/metrics/v1/metrics.proto#L79
 
     A gauge is an instantaneous measurement of a value.
 
@@ -102,9 +102,9 @@ class MetricDescriptor(object):
     """Defines a metric type and its schema.
 
     This class implements the spec for v1 MetricDescriptors, as of
-    opencensus-proto release v0.0.2. See opencensus-proto for details:
+    opencensus-proto release v0.1.0. See opencensus-proto for details:
 
-        https://github.com/census-instrumentation/opencensus-proto/blob/24333298e36590ea0716598caacc8959fc393c48/src/opencensus/proto/metrics/v1/metrics.proto#L53  # noqa
+    https://github.com/census-instrumentation/opencensus-proto/blob/v0.1.0/src/opencensus/proto/metrics/v1/metrics.proto#L59
 
     :type name: str
     :param name: The metric type, including its DNS name prefix. It must be

opencensus/metrics/export/time_series.py

@@ -17,9 +17,9 @@ class TimeSeries(object):
     """Time series data for a given metric and time interval.
 
     This class implements the spec for v1 TimeSeries structs as of
-    opencensus-proto release v0.0.2. See opencensus-proto for details:
+    opencensus-proto release v0.1.0. See opencensus-proto for details:
 
-        https://github.com/census-instrumentation/opencensus-proto/blob/24333298e36590ea0716598caacc8959fc393c48/src/opencensus/proto/metrics/v1/metrics.proto#L112
+        https://github.com/census-instrumentation/opencensus-proto/blob/v0.1.0/src/opencensus/proto/metrics/v1/metrics.proto#L132
 
     A TimeSeries is a collection of data points that describes the time-varying
     values of a metric.

opencensus/metrics/export/value.py

@@ -13,9 +13,9 @@
 # limitations under the License.
 """
 The classes in this module implement the spec for v1 Metrics as of
-opencensus-proto release v0.0.2. See opencensus-proto for details:
+opencensus-proto release v0.1.0. See opencensus-proto for details:
 
-https://github.com/census-instrumentation/opencensus-proto/blob/24333298e36590ea0716598caacc8959fc393c48/src/opencensus/proto/metrics/v1/metrics.proto
+https://github.com/census-instrumentation/opencensus-proto/blob/v0.1.0/src/opencensus/proto/metrics/v1/metrics.proto
 """  # noqa
 
 from copy import copy

opencensus/trace/tracestate.py

@@ -47,7 +47,7 @@ def append(self, key, value):
     # if the tracestate value size is bigger than 512 characters, the tracer
     # CAN decide to forward the tracestate
     def is_valid(self):
-        if len(self) is 0:
+        if len(self) == 0:
             return False
         # there can be a maximum of 32 list-members in a list
         if len(self) > 32: