automation: install python3-venv Debian package Debian's python install has a crippled venv by default, as it is lacking ensurepip. When you try to run `python3 -m venv` it tells you to install `python3-venv`. So this commit does that in our automation environment so we can fully test installing Mercurial using venv+pip with the system Python. Differential Revision: https://phab.mercurial-scm.org/D7229

# 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