PolicyLengthExceededException

[wangsha]

PolicyLengthExceededException occurs when schedule tasks

Context

same issue as aws/chalice#48

Expected Behavior

No duplicated statement in lambda policy.

Actual Behavior

Same statement appended to existing policy for each update.

Possible Fix

Check statement existance.

Steps to Reproduce

with any functioning zappa project

1. add following entry in zappa config. async_response_table=xxxx, async_source='sns', async_resources=true.
2. calling zappa schedule and observe policy keeps growning until hit PolicyLengthExceededException

Your Environment

• Zappa version used: 0.51.0
• Operating System and Python version: 3.7
• The output of pip freeze:
• Link to your project (optional):
• Your zappa_settings.json: