add flake8 pre-commit

CONTRIBUTING.md

@@ -0,0 +1,13 @@
+# Contributing guidelines
+
+## Pre-commit tidy/linting hook
+
+You'll need to install flake8 first.
+
+We use flake8 to perform additional formatting and semantic checking of code.
+We provide a pre-commit git hook for performing these checks, before a commit
+is created:
+
+```bash
+ln -s ../../tools/git-pre-commit .git/hooks/pre-commit
+```

requirements.txt

@@ -1,3 +1,4 @@
+flake8
 pyyaml
-typeguard
 tensorboardX
+typeguard

tools/flake8_hook.py

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+import sys
+
+from flake8.main import git
+
+if __name__ == '__main__':
+    sys.exit(
+        git.hook(
+            strict=True,
+            lazy=git.config_for('lazy'),
+        )
+    )

tools/git-pre-commit

@@ -0,0 +1,5 @@
+#!/bin/bash
+set -e
+
+echo "Running pre-commit flake8"
+python tools/flake8_hook.py