tox: Update pyflakes to 1.0.0.

Changes:

- Don't mark shadowing variable as 'used'.
- Test that used variable in loop is considered used
- Don't report UnusedImport when binding global name
- Support Python 3.5 async/await statements for Pyflakes.
- Use os.linesep for Windows compatibility
- os.chmod() supports only read-only flag operations on Windows

tox.ini

@@ -110,7 +110,7 @@ deps =
     -r{toxinidir}/requirements.txt
     py==1.4.30
     pytest==2.7.3  # rq.filter: <2.8.0
-    pyflakes==0.9.2
+    pyflakes==1.0.0
     pytest-flakes==1.0.1
 commands =
     {envpython} scripts/link_pyqt.py --tox {envdir}