What does it mean when Click exits with exit code 2?

This appears to indicate a usage error:

An internal exception that signals a usage error. This typically aborts any further handling.

This is consistent with Click's own tests, e.g.

• https://github.com/pallets/click/blob/123dd717439d8620d8d6be5574d2c9f007952326/tests/test_arguments.py#L82
• https://github.com/pallets/click/blob/123dd717439d8620d8d6be5574d2c9f007952326/tests/test_arguments.py#L190
• https://github.com/pallets/click/blob/123dd717439d8620d8d6be5574d2c9f007952326/tests/test_arguments.py#L201
• https://github.com/pallets/click/blob/123dd717439d8620d8d6be5574d2c9f007952326/tests/test_formatting.py#L157
• https://github.com/pallets/click/blob/123dd717439d8620d8d6be5574d2c9f007952326/tests/test_formatting.py#L177
• https://github.com/pallets/click/blob/123dd717439d8620d8d6be5574d2c9f007952326/tests/test_formatting.py#L193

I ran

result = runner.invoke(cli, ['sync'])

instead of

result = runner.invoke(cli, ['--debug', 'sync'])

So you need to specify the flag as entered via CLI, not only pass the parameters consumed by the function if you use @click.option.

Additionally, the I made a typo for one of the flags.

How to debug

1. Look at the parameters you pass to runner.invoke (simplest: print it)
2. Execute it via CLI (e.g. cli(['--debug', 'sync']))

In my case this gave me the message

Error: no such option: --sync  Did you mean --syncs?