Fix: Train loop config validation was run during trainer.predict

[kaushikb11]

What does this PR do?

Fixes:
While predicting, it was verifying the train_loop configuration.

Only necessary for the bug-fix release branch

Before submitting

• Was this discussed/approved via a GitHub issue? (not for typos and docs)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or internal minor changes/refactorings)

PR review

Anyone in the community is free to review the PR once the tests have passed.
Before you start reviewing make sure you have read Review guidelines. In short, see the following bullet-list:

• Is this pull request ready for review? (if not, please submit in draft mode)
• Check that all items from Before submitting are resolved
• Make sure the title is self-explanatory and the description concisely explains the PR
• Add labels and milestones (and optionally projects) to the PR so it can be classified

Did you have fun?

Make sure you had fun coding 🙃

[carmocca]

LGTM

Do you want to also open a PR to master with these changes and resolve this TODO?

https://github.com/PyTorchLightning/pytorch-lightning/blob/6a1414681107cf77d1ebeba86359df7b6668bf49/pytorch_lightning/trainer/configuration_validator.py#L43

[kaushikb11]

@carmocca Sure.

Wondering where should I do the Changelog update here.

[Borda]

Wondering where should I do the Changelog update here.

in Added section :]

[pep8speaks]

Hello @kaushikb11! Thanks for updating this PR.

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2021-03-16 16:19:18 UTC

[kaushikb11]

@Borda Your commit won't work. dataloaders is not defined. Reverting back.

[Borda]

@Borda Your commit won't work. dataloaders is not defined. Reverting back.

it shall be defined in the parameter, right?

[Borda]

what is the difference to #6543?