tests: silence pyflakes for thirdparty/concurrent
It is complaining about unused imports.
Differential Revision: https://phab.mercurial-scm.org/D3263
--- a/tests/test-check-pyflakes.t Mon Apr 09 12:19:37 2018 -0700
+++ b/tests/test-check-pyflakes.t Mon Apr 09 12:22:31 2018 -0700
@@ -17,6 +17,7 @@
> -X hgext/fsmonitor/pywatchman \
> -X mercurial/pycompat.py -X contrib/python-zstandard \
> -X mercurial/thirdparty/cbor \
+ > -X mercurial/thirdparty/concurrent \
> -X mercurial/thirdparty/zope \
> 2>/dev/null \
> | xargs pyflakes 2>/dev/null | "$TESTDIR/filterpyflakes.py"