Bump singer-python to v1.9.1

[migstopheles]

Description of change

~3 years ago, singer-python was patched to fix issues with the standard JSON encoder failing to encode Decimal types.

Bumping the version of singer-python to its max minor version (1.9.1) should fix this issue.

Example error

2020-03-13 01:00:54,987Z    tap - Traceback (most recent call last):
2020-03-13 01:00:54,987Z    tap -   File "tap-env/bin/tap-fullstory", line 9, in <module>
2020-03-13 01:00:54,987Z    tap -     load_entry_point('tap-fullstory==1.0.3', 'console_scripts', 'tap-fullstory')()
2020-03-13 01:00:54,988Z    tap -   File "/code/orchestrator/tap-env/lib/python3.5/site-packages/tap_fullstory/__init__.py", line 162, in main
2020-03-13 01:00:54,988Z    tap -     do_sync()
2020-03-13 01:00:54,988Z    tap -   File "/code/orchestrator/tap-env/lib/python3.5/site-packages/tap_fullstory/__init__.py", line 154, in do_sync
2020-03-13 01:00:54,988Z    tap -     sync_events()
2020-03-13 01:00:54,988Z    tap -   File "/code/orchestrator/tap-env/lib/python3.5/site-packages/tap_fullstory/__init__.py", line 146, in sync_events
2020-03-13 01:00:54,988Z    tap -     singer.write_record("events", event)
2020-03-13 01:00:54,988Z    tap -   File "/code/orchestrator/tap-env/lib/python3.5/site-packages/singer/__init__.py", line 61, in write_record
2020-03-13 01:00:54,988Z    tap -     write_message(RecordMessage(stream=stream_name, record=record))
2020-03-13 01:00:54,988Z    tap -   File "/code/orchestrator/tap-env/lib/python3.5/site-packages/singer/__init__.py", line 52, in write_message
2020-03-13 01:00:54,988Z    tap -     sys.stdout.write(message.tojson() + '\n')
2020-03-13 01:00:54,989Z    tap -   File "/code/orchestrator/tap-env/lib/python3.5/site-packages/singer/__init__.py", line 33, in tojson
2020-03-13 01:00:54,989Z    tap -     return json.dumps(self.asdict())
2020-03-13 01:00:54,989Z    tap -   File "/root/.pyenv/versions/3.5.2/lib/python3.5/json/__init__.py", line 230, in dumps
2020-03-13 01:00:54,989Z    tap -     return _default_encoder.encode(obj)
2020-03-13 01:00:54,989Z    tap -   File "/root/.pyenv/versions/3.5.2/lib/python3.5/json/encoder.py", line 198, in encode
2020-03-13 01:00:54,989Z    tap -     chunks = self.iterencode(o, _one_shot=True)
2020-03-13 01:00:54,989Z    tap -   File "/root/.pyenv/versions/3.5.2/lib/python3.5/json/encoder.py", line 256, in iterencode
2020-03-13 01:00:54,989Z    tap -     return _iterencode(o, 0)
2020-03-13 01:00:54,989Z    tap -   File "/root/.pyenv/versions/3.5.2/lib/python3.5/json/encoder.py", line 179, in default
2020-03-13 01:00:54,989Z    tap -     raise TypeError(repr(o) + " is not JSON serializable")
2020-03-13 01:00:54,989Z    tap - TypeError: Decimal('24.1444') is not JSON serializable

Manual QA steps

Risks

• minor version bump so no breaking changes expected

Rollback steps

• revert this branch

[cmerrick]

Hi @migstopheles, thanks for your contribution!

In order for us to evaluate and accept your PR, we ask that you sign a contribution license agreement. It's all electronic and will take just minutes.

[cmerrick]

You did it @migstopheles!

Thank you for signing the Singer Contribution License Agreement.

[migstopheles]

@cmerrick is this OK to be merged or are there more steps required?

[lbillingham]

Hello folks 👋 , I'm getting similar problems with Decimal conversions. Anything I can do to help with this PR?

[markshilton]

We could really, really do with getting this merged so we can use this tap properly. It's currently unusable for us without this fix. Is anyone able to help?

[migstopheles]

@dmosorast @KAllan357 @cmerrick sorry for the :postal_horn: but does anyone know how i can get this PR approved and merged? thanks

[markshilton]

Thanks for merging this @KAllan357. You've made a bunch of engineers and data scientists at TravelNest very happy! 😄