Build is failing because of bad pip dependency

[nmaludy]

@tchiapuziowong Looks the the build for this pack is failing to find the PyPI package pyaoscx: https://circleci.com/api/v1.1/project/github/StackStorm-Exchange/stackstorm-aoscx/3/output/103/0?file=true&allocation-id=5fa59913b270d70782b8e95d-0-build%2F53654357 (scroll all the way to the bottom)

Collecting pyaoscx>=0.2.1 (from -r /home/circleci/repo/requirements.txt (line 3))
  Could not find a version that satisfies the requirement pyaoscx>=0.2.1 (from -r /home/circleci/repo/requirements.txt (line 3)) (from versions: 0.1.1, 0.1.2, 0.2.0)
No matching distribution found for pyaoscx>=0.2.1 (from -r /home/circleci/repo/requirements.txt (line 3))

[nmaludy]

Looks like this pack only supports python3, so the python2 build was failing because the python dependencies can't be met on python 2.

Made a PR #2 to fix this.

TODO, we need to skip python2 builds for packs that only support python 3.