use better pre-commit hooks and fix lint.

examples/GAN/BEGAN.py

@@ -92,7 +92,6 @@ class Model(GANModelDesc):
             x = tf.cast(x, tf.uint8)
             tf.summary.image(name, x, max_outputs=30)
 
-
         with argscope([Conv2D, FullyConnected],
                       W_init=tf.truncated_normal_initializer(stddev=0.02)):
             with tf.variable_scope('gen'):
@@ -150,6 +149,7 @@ def get_config():
         max_epoch=400,
     )
 
+
 if __name__ == '__main__':
     args = DCGAN.get_args()
     if args.sample:

tests/dev/git-hooks/pre-commit

-#!/bin/sh
+#!/bin/bash -e
 flake8 .
-cd examples && flake8 .
+
+cd examples
+GIT_ARG="--git-dir ../.git --work-tree .."
+
+# find out modified python files
+MOD=$(git $GIT_ARG status -s | grep -E '\.py$'  | grep -E '^\b+M\b+' | cut -c 4-)
+flake8 $MOD