.editorconfig

packaging: update Ubuntu docker build dependencies to Python 3

Changeset 7574ccd87200f02e updated the Debian docker builds to Python 3. In doing
so, the Ubuntu docker-based builds broke, as the Dockerfile does not
include the new dependencies as specified in `contrib/packaging/debian/control`.

This commit changes the dependencies in the Ubuntu Dockerfile template
to their Python 3 equivalents, fixing `make docker-ubuntu-bionic`.

Differential Revision: https://phab.mercurial-scm.org/D7810

# See http://EditorConfig.org for the specification

root = true

[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true

[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true

[*.t]
indent_size = 2
indent_style = space
trim_trailing_whitespace = false