Change imports to a one-per-line style

This would prevent useless merge conflicts.

I think it would only need to add force_single_line = true to our isort configuration.

_Originally posted by @pradyunsg in https://github.com/pypa/pip/pull/6729#issuecomment-513418090_

And for the record, I’m in favor 😃

[pfmoore]

Good point re reducing the pain for external contributors. I’ll learn to live with the change, might even persuade me to improve my workflow, who knows? 😃

[pradyunsg]

FWIW, we’d probably use a style like:

from pip._internal.utils.misc import (
    _make_build_dir,
    ask_path_exists,
    backup_dir,
    call_subprocess,
    display_path,
    dist_in_site_packages,
    dist_in_usersite,
    ensure_dir,
    get_installed_version,
    redact_password_from_url,
    rmtree,
)

I’m almost certain that isort supports this as a mode in it – 3 or 5.

(I typed this on Monday morning, on my mobile, while walking to class. I’m weird.)

I see there was some discussion at #6729 so I figured it’d help to clarify.

/cc @pfmoore