tests: add flake8 check
This test will hopefully help prevent style errors. To be determined:
which errors / warnings to ignore?
--- a/tests/test-check-pyflakes.t Sun May 15 22:23:16 2016 -0300
+++ b/tests/test-check-pyflakes.t Tue Aug 30 14:05:36 2016 -0700
@@ -10,3 +10,6 @@
$ hg locate 'set:**.py or grep("^!#.*python")' 2>/dev/null \
> | xargs pyflakes 2>/dev/null
+run flake8 if it exists; if it doesn't, then just skip
+
+ $ type flake8 >/dev/null 2>/dev/null && hg files -0 'glob:**.py' | xargs -0 flake8 || true