Ignore IS NOT NULL statement

[kekekekule]

This solves the problem with django-pgtrigger which generates sql with "IS NOT NULL" condition and this becomes an error in a linter though it's not.

Sure this solves: #263

[kekekekule]

@David-Wobrock also maybe this fix could be backported to version 4.1.x of a linter? The version 5.0.0 has breaking changes and it's painful at the moment to migrate a project

[David-Wobrock]

Thanks for the PR!

My bad @kekekekule for closing the PR - I didn't get my head around GitHub permissions on forked repositories.
Anyway, I re-opened an updated version of the PR here #282, since I'm not able to push new commits onto your fork branch.

@David-Wobrock also maybe this fix could be backported to version 4.1.x of a linter? The version 5.0.0 has breaking changes and it's painful at the moment to migrate a project

I generally prefer not to backport fixes. I don't think the linter has enough adoption that it's worth the trouble.

Do you mean the fact that if sqlmigrate crashes, we also crash the linter?
If yes, would adding a configuration option to ignore crashes work for you? I recently encountered a case where I would have liked to ignore crashing migrations :) I think it would make sense.

[kekekekule]

@David-Wobrock yep, it would be nice if I had an option to ignore sqlmigrate crashes.