Add dataclasses to base Docker images. (#43217)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43217
Dataclasses is part of standard library in Python 3.7 and there
is a backport for it in Python 3.6. Our code generation will
start using it, so add it to the default library set.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Reviewed By: malfet
Differential Revision: D23214028
Pulled By: ezyang
fbshipit-source-id: a2ae20b9fa8f0b22966ae48506d4ddea203e7459
