[STYLE] run autopep8 and isort (#421)

Run:
```
isort ./python
autopep8 -i --ignore E501,E701,E731 $(find ./python/ -name '*.py')
```
with an `.isort.cfg` and then clean up a few warts. This PR should be a no-op; the idea is that this is all boring whitespace changes, and any config file changes will be in a different change to make it easier to review.

python/bench/run.py

@@ -1,7 +1,8 @@
 import argparse
-import sys
-import os
 import inspect
+import os
+import sys
+
 import triton