[Empathetic Dialogues] Switch to DialogTeacher

[EricMichaelSmith]

Patch description

• Switch EmpatheticDialogues over to DialogTeacher to allow for efficient eval of this dataset in distributed mode
• Delete an unused teacher and unused flags and Message keys
• Also switch EDPersonaTopicifierTeacher, a version of EmpatheticDialogues that includes personas, over to DialogTeacher

Testing steps

• Checked that the following pass:
  • pytest tests/tasks/test_empathetic_dialogues.py
  • pytest parlai/tasks/empathetic_dialogues/test.py
  • pytest parlai/tasks/blended_skill_talk/test.py
  • pytest tests/tasks/test_style_gen_teachers.py
• Compared the output of parlai dd -t empathetic_dialogues -v and parlai dd -t parlai.tasks.blended_skill_talk.agents:EDPersonaTopicifierTeacher before and after this PR

[stephenroller]

very nice! great cleanup and faster to boot!

[stephenroller]

in an ideal world we would make this entire function an iterator that didn't explicitly load data into memory, which speeds up parlai dd and lowers peak memory usage.

it's fine for this PR

[stephenroller]

Make sure you merge in master to get the fixes to CI, and check pytest parlai/tasks/empathetic_dialogues/test.py (which you seemed to skip since it has two sets of tests)

[EricMichaelSmith]

Make sure you merge in master to get the fixes to CI, and check pytest parlai/tasks/empathetic_dialogues/test.py (which you seemed to skip since it has two sets of tests)

Good point, checked

[tempdeltavalue]

ImportError: cannot import name 'EmpatheticDialoguesTeacher' from 'parlai.core.teachers'

[EricMichaelSmith]

Can you paste the command that gives that error?