Changing gym registration to be faster

[vincentpierre]

Motivation and Context

Using gym.auto_name forces us to parse all files, load them and check the auto_name value. This is very slow. This change makes it such that the auto_gym environments are defined in a dictionary PRE_REGISTERED_GYM_TASKS in gym_definitions.py

How Has This Been Tested

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have completed my CLA (see CONTRIBUTING)
• I have added tests to cover my changes.
• All new and existing tests passed.

[eundersander]

LGTM! Will people forget to add their new task to PRE_REGISTERED_GYM_TASKS? If a task lookup fails, can we print a pretty message with reminder to check PRE_REGISTERED_GYM_TASKS?

[vincentpierre]

The lookup is managed by gym so it will be hard to have custom error messages on missing environments. I do not expect users to register their environments this way, I would prefer they used make_gym_env as documented in the README.

[rpartsey]

I like these changes!

[rpartsey]

I would prefer they used make_gym_env as documented in the README.

@vincentpierre do you mean habitat.gym.make_gym_from_config?

[vincentpierre]

@vincentpierre do you mean habitat.gym.make_gym_from_config?

Yes, exactly.