Multiple event triggers generate duplicate copies of the first event trigger defined

Context

When I define event triggers like the following (contrived from my real usage):

base_stage:
...
  events:
    - function: summary_generator.generate
      event_source:
        arn:  arn:aws:s3:::some-bucket-us-east-2
        events:
          - s3:ObjectCreated:Post
    - function: summary_generator.generate2
      event_source:
        arn:  arn:aws:s3:::some-bucket-us-east-2
        events:
          - s3:ObjectCreated:Put

I get the following output on update:

Removed event summary_generator.generate (['s3:ObjectCreated:Post']).
Removed event summary_generator.generate2 (['s3:ObjectCreated:Put']).
Created s3:ObjectCreated:Post event schedule for summary_generator.generate!
s3:ObjectCreated:Put event schedule for summary_generator.generate2 already exists - Nothing to do here.

However, what actually happens is I get two event triggers defined on the lambda for the first event trigger definition. The number of event triggers created is equal to the number of event triggers defined (rather than the number of deploys).

This may be caused by my adding the second even definition after the initial deploy. It may work correctly if both events are defined when the zappa project is first deployed, but I have not tested that scenario.

Expected Behavior

Two event triggers are created according to my definitions.

Actual Behavior

Two event triggers are created, both matching the first event trigger definition.

Possible Fix

I haven't debugged this very far, but my guess is that the problem lies in the logic in zappa.utilitites.add_event_source, where there's a comment "# TODO: Detect changes in config and refine exists algorithm".

Steps to Reproduce

See above example of event definitions.

Your Environment

• Zappa version used: zappa 0.45.1
• Operating System and Python version: Mac, Python 3.6
• The output of pip freeze: argcomplete==1.9.2 asn1crypto==0.24.0 attrs==17.3.0 aws-xray-sdk==0.95 base58==0.2.4 boto==2.48.0 boto3==1.5.6 botocore==1.8.20 cairocffi==0.8.0 CairoSVG==2.1.2 certifi==2017.11.5 cffi==1.11.2 cfn-flip==1.0.0 chardet==3.0.4 click==6.7 cookies==2.2.1 coverage==4.4.2 credstash==1.14.0 cryptography==2.0.3 cssselect2==0.2.1 defusedxml==0.5.0 docker==2.7.0 docker-pycreds==0.2.1 docutils==0.14 durationpy==0.5 future==0.16.0 hjson==3.0.1 html5lib==1.0.1 idna==2.6 invoke==0.22.0 Jinja2==2.10 jmespath==0.9.3 jsondiff==1.1.1 jsonpickle==0.9.5 kappa==0.6.0 lambda-packages==0.19.0 MarkupSafe==1.0 mock==2.0.0 moto==1.1.25 olefile==0.44 pbr==3.1.1 pendulum==1.3.2 Pillow==4.3.0 placebo==0.8.1 pluggy==0.6.0 py==1.5.2 pyaml==17.12.1 pycodestyle==2.3.1 pycparser==2.18 PyPDF2==1.26.0 Pyphen==0.9.4 pytest==3.3.1 pytest-cov==2.5.1 python-dateutil==2.6.1 python-slugify==1.2.4 pytz==2017.3 pytzdata==2017.3.1 PyYAML==3.12 reportlab==3.4.0 requests==2.18.4 requests-mock==1.4.0 s3transfer==0.1.12 six==1.11.0 timeout-decorator==0.4.0 tinycss2==0.6.1 toml==0.9.4 tqdm==4.19.1 troposphere==2.1.2 tzlocal==1.5.1 Unidecode==0.4.21 urllib3==1.22 webencodings==0.5.1 websocket-client==0.45.0 Werkzeug==0.12 wrapt==1.10.11 wsgi-request-logger==0.4.6 xmltodict==0.11.0 zappa==0.45.1
• Link to your project (optional): n/a
• Your zappa_settings.py: example above