get_output_schema exception with table name

[AliSayyah]

get_output_schema will raise an exception with the name of the corresponding table if something goes wrong while generating the tables.
based on #447

Another alternative would be to add the errors attribute to the OutputSchema class and handle it like how warnings are being addressed.

[AliSayyah]

The test works in python 3.10 (and 3.9 in local) but not with 3.7.
I have to figure out what functionality changed in these versions.

[dantownsend]

I think something changed with mocks in > Python 3.7.

I've been caught out by this many times.

[AliSayyah]

https://docs.python.org/3/library/unittest.mock.html#unittest.mock.AsyncMock

I think this is it. create_table_class_from_db is an async function and mock handles it in >=3.8 as a coroutine.

[dantownsend]

@AliSayyah If you search for set_mock_return_value in the Piccolo codebase, there's something there which should help.

[codecov-commenter]

Codecov Report

Merging #449 (396c9ec) into master (b384f71) will decrease coverage by 0.10%.
The diff coverage is 73.68%.

@@            Coverage Diff             @@
##           master     #449      +/-   ##
==========================================
- Coverage   90.84%   90.74%   -0.11%     
==========================================
  Files         103      104       +1     
  Lines        6870     6902      +32     
==========================================
+ Hits         6241     6263      +22     
- Misses        629      639      +10     

Impacted Files	Coverage Δ
piccolo/apps/schema/commands/generate.py	88.96% <70.58%> (-2.47%)	⬇️
piccolo/apps/schema/commands/exceptions.py	100.00% <100.00%> (ø)

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[AliSayyah]

@dantownsend I think this is ready for review,

[dantownsend]

@AliSayyah Cool, thanks

[dantownsend]

@AliSayyah This looks great thanks.

I pushed a few extra commits:

• I decided to use your AsyncMock implementation everywhere, and removed set_mock_return_value, as I think your solution is more intuitive.
• I took this opportunity to improve error handling if indexes couldn't be parsed (related to piccolo schema generate crash on index parse.  #363)

[AliSayyah]

Thank you this is great!
I think adding a test for index_warnings could be a good idea. If you think it is necessary, I can add it tommorow.

[dantownsend]

@AliSayyah Yeah, it could do with a unit test really. I'm happy to release as is, but if you wouldn't mind doing a separate PR to add a test, that would be great.

[AliSayyah]

@AliSayyah Yeah, it could do with a unit test really. I'm happy to release as is, but if you wouldn't mind doing a separate PR to add a test, that would be great.

Yeah, I'll open another PR👍.

[dantownsend]

@AliSayyah thanks