Bug 1523562 [wpt PR 15031] - Update pyflakes to 2.1.0, a=testonly

Automatic update from web-platform-tests
Update pyflakes from 2.0.0 to 2.1.0
--
Fix comparison with int to use == rather than relying on interning

--

wpt-commits: bae08c312f922ab1517ef2e5a14588eadc8d02c0, 2603f1314ebda48d20e2645d34ae8dda413e3484
wpt-pr: 15031

testing/web-platform/tests/tools/requirements_flake8.txt

@@ -1,4 +1,4 @@
 flake8==3.6.0
 pycodestyle==2.4.0
-pyflakes==2.0.0
+pyflakes==2.1.0
 pep8-naming==0.7.0

testing/web-platform/tests/tools/wptrunner/wptrunner/metadata.py

@@ -509,7 +509,7 @@ class PackedResultList(object):
         prop = prop_intern.get((packed & 0xF000) >> 12)
 
         value_idx = (packed & 0x0F00) >> 8
-        if value_idx is 0:
+        if value_idx == 0:
             value = self.raw_data[idx]
         else:
             value = status_intern.get(value_idx)