test_default_battery_movement fails when battery feature is disabled

[bowlofeggs]

Describe the bug

I'm working on upgrading Gentoo to bottom-0.6.4, and I'm seeing one test that fails when the battery feature is disabled:

---- test_default_battery_movement stdout ----
thread 'test_default_battery_movement' panicked at 'called `Result::unwrap()` on an `Err` value: ConfigError("\"battery\" is an invalid widget name.\n\nSupported widget names:\n+--------------------------+\n|            cpu           |\n+--------------------------+\n|        mem, memory       |\n+--------------------------+\n|       net, network       |\n+--------------------------+\n| proc, process, processes |\n+--------------------------+\n|     temp, temperature    |\n+--------------------------+\n|           disk           |\n+--------------------------+\n                ")', tests/layout_management_tests.rs:47:14
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

What operating system/architecture are you using?

This is a Gentoo container in podman on x86_64 (host is Fedora 33, though that's probably not relevant).

What terminal are you using bottom on?

gnome-terminal, though this is probably not relevant.

What version are you on?

0.6.4.

How did you install bottom?

I am building bottom from the 0.6.4 tag with Rust 1.53.0.

How can we reproduce this?

Run cargo test --no-default-features.

What is the actual behaviour?

See error output in Description above.

What is the expected behaviour?

Tests should pass, or automatically skip in environments they can't pass in.

[bowlofeggs]

I wonder if this test should be feature gated on the new battery feature.