Major changes

• Added v4 mujoco environments that use the new deepmind mujoco 2.2.0 module. This can be installed through pip install gym[mujoco] with the old bindings still being available using the v3 environments and pip install gym[mujoco-py]. These new v4 environment should have the same training curves as v3. For the Ant, we found that there was a contact parameter that was not applied in v3 that can enabled in v4 however was found to produce significantly worse performance see comment for more details. @Rodrigodelazcano
• The vector environment step info API has been changes to allow hardware acceleration in the future. See this PR for the modified info style that now uses dictionaries instead of a list of environment info. If you still wish to use the list info style, then use the VectorListInfo wrapper. @gianlucadecola
• On gym.make, the gym env_checker is run that includes calling the environment reset and step to check if the environment is compliant to the gym API. To disable this feature, run gym.make(..., disable_env_checker=True). @RedTachyon
• Re-added gym.make("MODULE:ENV") import style that was accidentally removed in v0.22 @arjun-kg
• Env.render is now order enforced such that Env.reset is required before Env.render is called. If this a required feature then set the OrderEnforcer wrapper disable_render_order_enforcing=True. @pseudo-rnd-thoughts
• Added wind and turbulence to the Lunar Lander environment, this is by default turned off, use the wind_power and turbulence parameter. @virgilt
• Improved the play function to allows multiple keyboard letter to pass instead of ascii value @Markus28
• Added google style pydoc strings for most of the repositories @pseudo-rnd-thoughts @Markus28
• Added discrete car racing environment version through gym.make("CarRacing-v1", continuous=False)
• Pygame is now an optional module for box2d and classic control environments that is only necessary for rendering. Therefore, install pygame using pip install gym[box2d] or pip install gym[classic_control] @gianlucadecola @RedTachyon
• Fixed bug in batch spaces (used in VectorEnv) such that the original space's seed was ignored @pseudo-rnd-thoughts
• Added AutoResetWrapper that automatically calls Env.reset when Env.step done is True @balisujohn

Minor changes

• BipedalWalker and LunarLander's observation spaces have non-infinite upper and lower bounds. @jjshoots
• Bumped the ALE-py version to 0.7.5
• Improved the performance of car racing through not rendering polygons off screen @andrewtanJS
• Fixed turn indicators that were black not red/white in Car racing @jjshoots
• Bug fixes for VecEnvWrapper to forward method calls to the environment @arjun-kg
• Removed unnecessary try except on Box2d such that if Box2d is not installed correctly then a more helpful error is show @pseudo-rnd-thoughts
• Simplified the gym.registry backend @RedTachyon
• Re-added python 3.6 support through backports of python 3.7+ modules. This is not tested or compatible with the mujoco environments. @pseudo-rnd-thoughts